Opal is a well-known example of a mineral whose color is caused by a physical phenomenon called “diffraction.” Other phenomena include iridescence, a rainbow effect seen in iris quartz and pearls; chatoyancy, which we see in cat’s-eye stones and some malachite; asterism, which is displayed in star stones; aventurescence, as seen in aventurine quartz and sunstones; adularescence, seen in moonstone; and play of color, or the alexandrite effect, seen in the alexandrite variety of chrysoberyl and some garnets. In every one of these groups, the cause of the color is related to some internal physical structure and not a metallic impurity or element in the mineral’s structure.

Opal Color

For centuries, people tried to explain the play of color seen in many opals. Finally, in the 1960s, we developed equipment that could actually see the internal structure of opal. It revealed a very orderly arrangement of submicroscopic spherules of silica. These spherules and the spaces between them acted as a diffraction grating, spreading light into its various colors. The sizes of these spherules and the angle the light struck them, coupled with the viewer’s angle, determined which color wavelengths were canceled and which ones were reflected. Diffraction of light results in opal’s play of color.

Labradorite Color

A more common mineral that gets its play of color from diffraction is the feldspar mineral labradorite. This mineral can develop in huge formations, resulting in outcrops that give off flashes of color.

Labradorite crystallizes in thin wafers in parallel layers that repeat to form a diffraction grating. This has the effect of separating light into its colors, giving labradorite a play of color that depends, in part, on the angle of the source of light. The thickness of each crystal and each cluster of crystals in their parallel layers also affect which color is seen. Labradorite can flash bronze, blue, green, and in some cases, red or violet in an overall groundmass of gray to blue. It is thought the gray color of the groundmass is due to the scattering of light by the internal structure.

Play of Color

Another attractive feldspar mineral is adularia. Like labradorite, it develops as thin crystals that line up in parallel arrangement and act as a diffraction grating. But adularia does not show a play of color. The twinned arrangement of the crystals simply scatters light. While it can also be shades of gray, pink, peach, green and brown, it is best known for a bluish-white color that is reminiscent of the moon.

Properly cut adularia gives off a cloudy sheen that seems to float throughout the polished stone. We give this lovely form of adularia the name “moonstone.”

Why does adularia have little color, while labradorite is a riot of color? Minerals color variations are because of minor variations in the refractive index of the labradorite crystals involved. In adularia, the refractive indices of the crystals are virtually the same.

Iridescence

Iridescence is described as a play of changing colors on a surface of a mineral. A prime example is the look of oil spread over the surface of water. The oil particles have a different refractive index than the water, and this physical difference results in a play of color.

The most common example of this phenomenon is called “peacock ore”, which is actually the mineral bornite (copper sulfide). A freshly broken surface of bornite quickly oxidizes, forming a thin oxide mineral layer whose refractive index differs from bornite’s and creates a play of color. More subdued examples of this iridescence are seen on some crystal surfaces of pyrite, cuprite, chalcopyrite and hematite.

Pearl Iridescence

Iridescence is what gives pearls their soft, moonlike luster, called “orient.” Pearls are made up of layer upon layer of microscopic crystals of hexagonal aragonite. The refractive indexes of these layers are the same. Colored and black pearls result from inclusions that get into the pearl’s structure.

Mother of Pearl’s lovely shimmer, or glow, comes from the interior lining of shells, which is made up of two different substances: the calcium carbonate mineral aragonite, which forms microscopic hexagonal crystals, and conchiolin, a fibrous protein that forms in layers in parallel arrangement. The parallel fibers of the conchiolin are the key to creating the iridescence we see in mother of pearl, also called “nacre.”

Chatoyancy

When the fibers of a mineral develop in a parallel arrangement, they impart a silky shimmer or glow of light, called chatoyancy, that can be very appealing. You can expect to see this shimmer in a range of minerals. Asbestos is a very common example. When the asbestos is invaded by silica, it can form what we normally call tiger’s-eye, which is a very useful chatoyant gemstone with a silky luster. The invading silica negates the hazard we normally associate with asbestos.

Iridescence Within Stain Spar

One variety of gypsum, called stain spar, also shows iridescence, or glimmer of light. The mineral looks like silk cloth, whose fibers are also arranged in a tightly woven, parallel structure. Another example of iridescence is seen in some malachite. This copper carbonate usually crystallizes in tightly packed needles, which grow in slightly diverging radiating masses. When freshly broken, these near-parallel fibers give off a shimmering green color.

Asterism is seen in minerals like diopside, gem corundum, some moonstones, and several others. In these species, included fibrous crystals of the mineral rutile, in an intersecting arrangement, reflect light in a six-rayed star pattern. This physical phenomenon is what creates rare star sapphires and rubies, which are very valuable varieties.

Cat’s-eye gems exhibit chatoyancy, as well as a single, bright, linear reflection from tightly packed parallel fibers of a second mineral. Lapidaries give these gemstones a slight to strong dome and orient them so that the included mineral, often rutile or tourmaline, runs straight across the curved surface to form a single bright line, much like the vertical iris in a cat’s eye. It is important to know that these included needle crystals are all oriented along just one of the several growth axes of the hexagonal corundum stone.

Hexagonal Minerals

Hexagonal minerals like ruby and sapphire develop along four axes: one vertical “C” axis, from which three axes develop at right angles to the “C” axis, 60º from each other. For a star gem to form, the included mineral orients along the two arms of each horizontal axis to create a six-rayed star.

Chatoyancy is also seen in the cubic mineral gem garnet. The difference is that garnets form in the cubic system so the “star” forms from needle crystals that have oriented along the two horizontal axes that make up the cube form. Only two axes extend away from the single vertical axis, so the four arms of these axes with their parallel, included needles can orient to form a four-rayed star.

Understanding Aventurescence

Aventurescence is another physical phenomenon that involves inclusions. In this case, the inclusions are usually large enough to be visible and are scattered throughout the crystal mass, rather than oriented in a particular alignment. These scattered inclusions act as reflectors that scatter the light entering the host mineral.

An intriguing example of this is the manmade material called “goldstone”, which is glass with copper inclusions that give the glass a bright reddish-gold color.

Aventurescence is named for a quartz variety called aventurine, which is a lovely green color thanks to included chrome mica. These tiny, green flakes, or spangles, are scattered throughout the quartz, giving it a diffused green color of varying intensity that is very attractive.

The most attractive gem that falls into this category is the feldspar variety sunstone. This very lovely gem is found in several places in Oregon and shows a fine orange to red color due to included copper diffused throughout the gem. In some examples, the copper orients within the feldspar so that wisps and feathers of color are prominent in the gem. Sunstone claims in Oregon are occasionally opened to collectors for a fee.

Alexandrite Effect

Finally, the alexandrite effect is seen in very few minerals whose color is based on the type of light source. The chrysoberyl variety alexandrite is the obvious example.

Alexandrite has a light absorption band that, in sunlight, can split light into two different transmission areas. Under sunlight and fluorescent light, some of the blue wavelengths are absorbed, so green becomes dominant. When seen under in incandescent light, alexandrite is red.

As you collect colorful minerals, be aware that not all of them owe their color to a trace element inclusion. This is another area of interest you can pursue as you enjoy our wonderful hobby.

This story about what gives minerals color appeared in Rock & Gem magazine. Click here to subscribe. Story by Bob Jones.

The post What Gives Minerals Color? first appeared on Rock & Gem Magazine.

What is the difference between a mineral and a rock? A rock is an aggregate or mix, of one or more minerals. Here are some fun facts about minerals to enjoy…

René Just Haüy

2022 was the bicentennial of the death of René Just Haüy (2/28/1743 – 6/3/1822). Not a name many of us know, but Haüy was a French mineralogist and is important because he is known as the Father of Modern Crystallography. He studied crystal structure, applied his theories to mineral classification and wrote several books including the Traité de Minéralogie.

To honor him and the importance of minerals in our world, the International Mineralogical Association named 2022 the Year of Mineralogy.

What are Mineralogy & Crystallography?

Mineralogy is the study of everything about minerals including their crystal structure, physical and chemical properties. Crystallography is the study of the structure and properties of crystals.

How Minerals Are Formed

Minerals are formed in four main ways:

• From Magma – Hot, molten lava cools and crystallizes to form minerals such as topaz.
• From Water – Chemicals in saturated water precipitate, or separate, into solids. An easy example is salt, halite, that’s left behind after ocean water evaporates.
• Alteration – As minerals react, slowly or quickly, with their environment they form different minerals. Cuprite forms when it’s exposed to oxygen.
• Metamorphism – Exposure to heat and pressure alters the chemistry of a mineral to become a different mineral such as rubies.

Glorious Gemstones

Gemstones used for jewelry can be considered at the top of the mineral world. They are rare, valuable, popular and prized for their mineral colors which can be quite vivid once they are cut and polished.

FYI – Not all gemstones come from minerals, for example, pearls and amber. Gems can be precious meaning they are the rarest and most valuable. There are only four precious gems; diamonds, rubies, emeralds and sapphires. Gems that are also popular for jewelry but not as rare are called semiprecious…think amethyst, agate and turquoise.

The rating of precious or semiprecious was made long ago. Today, some semiprecious stones can be worth more than precious stones. Also, it doesn’t take into account scientific classifications of minerals. For example, emeralds are a type of beryl. Aquamarines are also a type of beryl.

Fabulous Diamonds

The word diamond comes from the Greek word adamas which means “invincible.” That’s certainly an accurate description given that diamonds have a Mohs hardness of ten!

According to National Geographic Kids Weird but True Rocks & Minerals, “On Earth’s surface, diamonds are rare. But go down around 100 miles below the surface and it’s a different story. Some scientists have estimated there may be more than a quadrillion tons of diamonds locked in rocks in Earth’s interior.”

This story about celebrating minerals appeared in Rock & Gem magazine. Click here to subscribe. Story by Pam Freeman.

The post Celebrating Minerals first appeared on Rock & Gem Magazine.

The rocks that animals consume are called gastroliths which literally translates to “stomach stones.” Gastroliths can be found in a range of animals including birds, reptiles, fish, insects, and even some mammals. Any type of stone can become a gastrolith; it just has to have been swallowed to join that club.

Why Do Animals Eat Rocks – Herbivores

What is an herbivore? It’s an animal that primarily eats plants. (Did you know that rocks and minerals play a role in plant growth?) So why do animals that eat rocks include herbivores? Though animals that eat stones are not all herbivores, those that are, have a special reason to consume rocks. Plant material is made up of cellulose. Cellulose is one of the most abundant, yet hard-to-digest materials found in plant material.

Cellulose is difficult to break down inside the body with only stomach acid. Why do animals eat rocks? Because stones inside an animal’s gizzard help to break this material down further before transferring it to a second stomach for additional digestion. This process smooths the stones over time. Many animals then regurgitate these smooth stones in favor of more jagged ones to help with the breaking down of food.

Why Birds Eat Rocks

Birds are the most common group of animals that eat rocks. These rocks aid in their digestion. Folks who raise birds are familiar with this as many supplement their feathered friends’ diets with grit, which are very small stones with uneven, blunt edges.

Birds don’t have teeth, or stomachs like mammals, instead, have a gizzard which is a muscular mass attached to their version of a stomach. The gizzard is where their food is ground up and mashed with the aid of the stones that they have swallowed.

Most avian consumers of stones are ground-dwelling or flightless birds. Chickens, turkeys, ostriches, and even penguins routinely swallow jagged little rocks while they are out and about foraging for food to help their digestion. Research has found that in ostriches, between one-fifth and one-half of their stomach contents are gastroliths.

These account for about one percent of the bird’s total body mass. It is speculated that the ratios and percentages are similar for other birds too (at least the ones that eat rocks).

There are some flying birds though that have been documented to be stone-eaters.

Crows and parrots are known to eat small rocks to aid their digestion. Some swimming and flying birds like ducks are also known to eat small grit-stones to help them break up their swallowed food. It is very likely that all birds swallow stones in some capacity to help break down their food.

Why Reptiles & Amphibians Eat Rocks

The need for birds to swallow rocks is pretty well understood. The same cannot be said though for reptiles. The prevailing theory for decades was that for swimming reptiles like crocodiles, swallowing rocks helped with their buoyancy. Given that they like to hover just below the water’s surface, this might be a plausible reason. A bellyful of rocks could help weigh themselves down enough so they don’t float all the way up to where they can be easily seen by their prey.

Much recent research about why do animals eat rocks, however, has suggested other hypotheses for this behavior in reptiles. Scientists have found that gastroliths make up less than two percent of the body mass of reptiles. They calculate that for the gastroliths to have the previously believed effect of achieving buoyancy, that number should be more than six percent of the animal’s body mass. The act of breathing, filling, and emptying their lungs with air, has more of an effect on buoyancy than the two percent of their body weight comprised of stones.

Current speculation about why do animals eat rocks is that the swallowed rocks help to stabilize the reptiles’ bodies in the water, reducing the tendency to roll from side to side. Though not reptiles, frogs eat rocks too.

Like birds though, the hypothesis is it helps them break up the insects they eat to get more nutrients from them. Earthworms are another animal that consumes rocks. Their internal digestive muscles, along with teethlike structures known as “grinders” break up plant material so that nutrients can be extracted from them.

Why Do Animals Eat Rocks – Sea Life

A variety of sea life eats rocks. Fish, clams, seals, and even whales are known to eat rocks, though in some cases it is believed to be inadvertent. Like crocodiles, it was once thought that sea lions, seals, walruses, and whales swallowed rocks to make diving easier.

Like other hypotheses that have arisen in recent years, the thinking for these sea creatures is that since many find their food on the ocean floor, they inadvertently scoop up rocks while scooping in on their food. This is seemingly more probable than swallowing rocks to help them dive.

The problem with the rocks as a diving aid hypothesis is that they would have to swallow huge rocks to make a difference. There is no evidence that they seek out and swallow big, heavy rocks.

Several species of bottom-feeding fish are also known to eat rocks, though again, it is not entirely known if this is intentional to aid in digestion, or accidental consumption while grabbing food off the seafloor. Other possibilities have arisen to explain this phenomenon in swimming mammals.

Alleviate Hunger

It is possible that some of these, and possibly other animals that eat rocks, do so to help alleviate hunger. Taking up space in their stomachs could potentially make them feel more full. Another conjecture is that they, like birds with their gizzards, swallow rocks to help their digestion (sans gizzard) and to break down the wide range of items that they may accidentally swallow.

One of the more unusual sea-dwelling rock eaters is a type of clam found in the Philippines, Lithoredo abatanica. The name roughly translates to “rock shipworm from the Abatan River.” Many would not recognize this animal as a clam.

It is fattened, worm-like, translucent, at least four inches (10 cm) long, with a shell complete with shovel-like projections. It is not akin in either appearance or bloodline to the familiar Quahog or Atlantic type of clam, but instead is a member of the shipworm family. These clams eat wood, but the newly discovered Lithoredo abatanica eats limestone, not wood. It burrows into rock and excretes sand. It is not yet known if these creatures actually derive any nutrition from these rocks.

The consumption of gastroliths by animals is a more common practice than most people would realize. Whether it be for digestion (with or without a gizzard), buoyancy, diving, deriving minerals, or feeling full, it is a widely practiced behavior in the wild animal kingdom. The next time you see a small, unassuming, round stone on the ground, it may well have been on quite a journey inside of any number of animals before finding itself at your feet.

This story about why do animals eat rocks previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Chris Bond.

The post Why Do Animals Eat Rocks? first appeared on Rock & Gem Magazine.

Sapphire

One of the official state gemstones of Montana, sapphires hold a special place in the Treasure State where they are readily found. Sapphires and rubies are both corundum, an aluminum oxide mineral typically found in crystalline form. The only difference between the two is the presence of chromium. If the corundum is red, it’s ruby. Otherwise, it’s always a sapphire.

One of the most desired types of gemstones, the most well-known sapphire hue is deep blue, but these gemstones are found in pink, green, violet, orange, purple and even brown. When they’re not blue, they’re referred to as fancy sapphires. These colors are because of the varying degrees of chromium, titanium oxide and iron within the stones. Sapphires also possess a trait called asterism where needle-like inclusions create the appearance of a six or twelve-patterned star. Beyond this unique characteristic appreciated by faceters, sapphires have a Mohs Amy Grisak; Getty Images/Science Photo Library value of nine, just below a diamond, making them extremely durable and an excellent choice for jewelry.

Tiger’s Eye

This distinct gem has a long history of fending off the “evil eye,” with its resemblance to a cat’s eye. In gemology, this trait is called chatoyancy, a French term meaning “shining like a cat’s eye.” When there are crocidolite (blue asbestos) fibers within cabochon-cut gemstones running parallel to each other, the rounded surface allows the light to reflect in a way that gives the tiger’s eye its signature look. Originally, scientists thought this phenomenon occurred when the crocidolite within the stone was changed by iron oxide and replaced with silica. But even though the coloration comes from this process, some researchers believe it’s actually crocidolite inclusions within columns of quartz within the stone that form the distinct paralleling nature.

Regardless of how it formed, tiger’s eye is a favorite gem for tumbling and with a Mohs value of seven, it’s a versatile stone for a multitude of uses. While it’s a ubiquitous stone these days, in the 1870s a single carat of tiger’s eye was worth an ounce of gold.

Unakite

Unakite is a terrific example of when a gemstone is a true rock as this beautiful pink and green specimen is a composite of metamorphic rocks including orthoclase, epidote and milky quartz. It’s formed during hydrothermal metamorphosis when the epidote replaces the silicate minerals, primarily plagioclase, within the granite. The epidote is green within unakite, while the pink orthoclase feldspar and quartz create the colorful speckling.

First found in the Unakas Mountains of Western North Carolina and Eastern Tennessee, it’s sometimes found in the rivers of the region, along with the beaches of Lake Superior where glaciers deposited the metamorphic rocks. With a Mohs rating of six to seven, unakite is among the types of gemstones that tumble well. It has been used to make small sculptures or is cut for jewelry. As eye-catching as it is, unakite is also valuable in construction on many levels, including being used as trim along the front steps of the south entrance of the Smithsonian National Museum of Natural History. It is also sometimes used less visibly as crushed stone in highway construction.

Vesuvianite

Sometimes called idocrase, vesuvianite was originally found along Mount Vesuvius in Italy, which buried the nearby inhabitants of the city of Vesuvius on August 24 in 79 AD, ironically during the festival of Vulcanalia, the god of fire. In the world of gem cutting, vesuvianite often refers to the rough stone, while the faceted gems are called idocrase.

Regardless of the name, this is a calcium-aluminum-silicate mineral that forms in a tetragonal structure. Its most popular colorations range from yellowish green to brownish or olive green, although there is a blue version called cyprine that derives its color from trace amounts of copper. With a Mohs value of six, vesuvianite isn’t a very hard stone and is often used for larger jewelry and sculptures. In its green coloration, it’s sometimes mistaken for other types of gemstones like peridot, although vesuvianite is far rarer.

White Topaz

While topaz is found in practically the entire color range, the white topaz is the clear version and boasts a similar appearance to a diamond. Outside of cost, there are distinct differences between the two types of gemstones. Topazes and diamonds are closely alike in clarity and color, but brilliance is where diamonds shine. Hardness is another determining factor. Diamonds reign supreme rating at Mohs 10, while topazes register as a Mohs eight, considerably less durable with a greater risk of scratching.

Topaz is created when water and magma react during the metamorphic process creating pegmatite featuring natural topaz that is typically initially clear. While the wide variety of colors is because of impurities, such as chromium replacing the aluminum within the stone, white topaz is the gem in its purest form. Specific hues are also created with heat, irradiation or the application of metal oxides to enhance colors. Topaz also exhibits pleochroism where the gem exhibits different colors depending on its angle, although the white topaz tends to remain consistent in its coloration.

Xenotime

On occasion, there are types of gemstones cut from this rare earth mineral, often found in yellowish-orange to reddish-brown hues, although high enough quality stones to facet are rare.

Like topaz, xenotime is found in pegmatite formations, as well as igneous rock and gneiss. Uranium and thorium are often found within this stone, creating natural radioactivity, although it is more commonly seen as a source for the transition metal yttrium, which is used as an alloy in the production of camera lenses and lasers. Its name is derived from the Greek terms for “vain” and “honor” in an early scientist’s snarky rebuke of another. Initially, Swedish chemist Jöns Jacob Berzelius believed he discovered a new element within the xenotime. This turned out to be the already known yttrium, which prompted mineralogist François Sulpice Beudant to throw down a bit of shade on the claim.

Yellow Kunzite

True gemologists might shudder at the inclusion of yellow kunzite in this types of gemstones list, but it’s an example of when marketing can be misguided. As a rule, kunzite is a pink to light purple variety of spodumene, a lithium-rich mineral found, once again, in pegmatite formations. Manganese gives kunzite those attractive colors. When the gem is yellow, it’s typically just called yellow spodumene. The name change might be a matter of one word sounding more appealing than the other, but it is still misleading as kunzite implies a specific hue. With a Mohs value of six and a half to seven, it is not a very durable gemstone, but it’s possible to find specimens of 20 carats or more. Spodumene, in general, is an important source of lithium, which is critical for car batteries, phones and medicine. It is mined in Afghanistan, Pakistan, California, North Carolina and South Dakota.

Zircon

Not to be confused with the synthetic cubic zirconia, zircon earned its place as a popular gemstone 2000 years ago. Found in sand and as part of many of the rocks throughout the world, zircon is one of the oldest minerals on earth. Because of its uranium content, scientists in Australia dated it back 4.4 million years. Not all zircons are radioactive, but those that are can be heat-treated to stabilize the integrity of the stone by slowing the degradation of the crystalline structure. In their natural form, zircons are found in colors ranging from clear to yellow, green, purple, brown and grays, which are typically caused because of radiation or impurities. Blue zircons, which have been popular since Victorian times, are created through heat treatments.

This story about types of gemstones by letter appeared in Rock & Gem magazine. Click here to subscribe. Story by Amy Grisak.

The post Types of Gemstones By Letter (S-Z) first appeared on Rock & Gem Magazine.

This is the first in a three-part series also covering types of gemstones with the letters J to R and types of gemstones with the letters S to Z.

What is a Gemstone? The definition of a gemstone isn’t quite as precise as the faceted beauties it describes. In general, when minerals, and sometimes organic materials such as amber, are cut and polished to create jewelry, we call them gemstones. There are nuances and outliers because some types of gemstones are too delicate to be worn, but most people in the gem world accept this general concept. To further clarify, types of gemstones are divided into “precious and semi-precious” stones with only diamonds, emeralds, sapphires and rubies encompassing the precious category. Everything else falls into the semi-precious zone, although this doesn’t necessarily imply inherent modern value or desirable characteristics. Regardless of the classification, there’s no question that when we can bring out the inherent beauty within these stones, it is something to be truly prized.

Agate

Agate is a silica-based mineral and is a popular semiprecious stone because of its attractive coloration and banding. Reportedly discovered by Greek philosopher Theophrastus roughly 2500 years ago, early people throughout the Middle East, Russia, and Greece used agates to create ornaments. According to research by the Bureau of American Ethnology, Indigenous People utilized them in much the same way.

Agate is a chalcedony, which is a type of cryptocrystalline quartz. Like many stones in this category, it’s created when groundwater seeps into the igneous rock where silica deposits form concentric layers within the rock cavities and crevices to create the telltale banded patterns.

The wide variety of colors, ranging from brown, black, white, red, gray, pink and yellow, are because of impurities in the groundwater. With a seven on the Mohs rating, agates are on the upper end of the hardness scale. This makes this translucent stone a favorite for rock tumbling. It’s often used for jewelry as well.

Bloodstone

An opaque, dark green type of gemstone, bloodstone features distinctive orange to scarlet red splatters that look like blood at first glance. This is the telltale signature of this traditional birthstone for March. The more modern birthstone choice is aquamarine.

Bloodstone is also called heliotrope, a name derived from the Greek helio meaning sun and tropos meaning toward the sun. If you garden, you’re familiar with heliotrope plants that turn toward the sun as they grow. This name indicates how the stone reflects the light. Along with legends of healing powers, bloodstone is also known as a protective stone. People will often wear or carry bloodstones to keep threats at bay.

The minerals chlorite and amphibole are responsible for the deep green coloration while iron oxide inclusions create the blood-red speckling.

Carnelian

Carnelian is one of the least expensive chalcedonies, the translucent yellow-orange to rich amber or even reddish-brown gems darken when heat treated. This includes the heat of the sun, so it’s best to keep your stone out of the sun to keep the color true. Iron is responsible for the red coloration and it’s what oxidizes and deepens when exposed to heat.

Carnelian is sometimes confused with jasper, although jasper is a type of gemstone that is typically a deep red and is opaque, rather than translucent. Plus, jasper often exhibits banding patterns on its surface appearance.

Carnelian is found throughout the world with some of the highest quality stones found in Scotland, Brazil and Washington State.

Even though it’s relatively inexpensive, many so-called carnelians are dyed and heat-treated agates. To determine if a carnelian is real, hold it up to the light. If it’s a natural carnelian, it looks cloudy. If it’s a heat-treated agate, it will most likely show striping.

Dumortierite

Although colors range from brown, green, and the rarer violet and pink, the eye-catching denim blue of this type of gemstone is probably the most popular with gemstone enthusiasts.

An aluminum boro-silicate mineral, dumortierite occurs in regions of high metamorphic activity that are also rich in aluminum and boron. Manganese, iron, and sometimes zinc inclusions, are responsible for the blue coloration.

Dumortierite was first described in 1881 after being found in the French Alps. It was named for the French paleontologist, Eugene Dumortier.

Dumortierite has a glassy (vitreous) luster. Its fibrous nature creates fine, almost hair-like radial crystals within the structure. The blue variation is sometimes mistaken for lapis lazuli, but dumortierite is typically a deeper blue or violet, plus lapis lazuli sports white or gold metallic flecks because of the pyrite within it.

Dumortierite quartz is quartz with inclusions of dumortierite.

Emerald

The birthstone for May, emeralds are a type of gemstone that earns their place as an adjective to describe a particularly intense green. The name is derived from the Greek word smaragdos, meaning green stone.

Created in metamorphic rocks when hot magma flowed over and through the crevices of limestone and shale, emeralds are a beryllium aluminum silicate. Although emeralds are a type of beryl, not all beryls are emeralds. While green beryl is still green, it’s distinctly lighter.

Chromium oxide is responsible for the emerald’s deep green. Other gems, such as peridot and tsavorite garnets, are also found in green hues but not with the same vibrancy. Registering 7-8.5 on the Mohs hardness scale and forming in hexagonal crystals, emeralds are long favorites for precious jewelry, but fakes abound. To determine authenticity, inspect the stone with a 10X loop. Flaws and inclusions, particularly a small crystal within the stone, indicate a natural emerald. Air bubbles or even a “too perfect” stone are tell-tale signs that it is not real.

Fluorite

Made of calcium fluoride, pure fluorite is colorless, yet samples are commonly found in shades of purple, golden-yellow, green, blue, pink and brown. These types of gemstones are translucent to nearly transparent with attractive banding. The term “fluorescence” became part of the terminology when physicist Sir George Gabriel Stokes was working with fluorite in 1852. Although fluorescence doesn’t consistently occur, fluorite is known to glow when there is the presence of uranium, yttrium and other rare earth elements. It often emits blue, although yellow, green, white and red shades are possible.

Also called fluorspar, it’s been produced in Illinois since the 1800s and is the state mineral. Often forming in cubic crystals, it is popular for jewelry but has a wide number of commercial applications ranging from an ingredient in ceramics to a flux used in refining metals.

Garnet

Many people picture garnets as red stones, but these types of gemstones are also found in shades of orange, pinkish-orange, green, reddish-purple, colorless and even blue and green, albeit these last two are rarer.

Garnets are formed when aluminum-laden sedimentary rock is metamorphosed. Garnets are one of the most widespread types of gemstones throughout the world. While the bulk of garnets is mined for industrial applications, it’s one of the oldest known gemstones and has been used for ornamental purposes for 5000 years. Historical evidence shows stones within the necklaces of pharaohs. Garnet signet rings were used by Roman leaders to seal documents.

Sometimes mistaken for a ruby, garnets are usually a darker red with brownish tones. When it’s held up to the light, yellow bands are often visible in a garnet while a ruby will be clear.

Hematite

Consisting of 70 percent iron, hematite is one of the primary ores of iron. Fortunately, it is one of the most abundant minerals on Earth. According to NASA, it’s also the most abundant mineral on Mars. The iron-rich environment is why Mars is dubbed the “red planet.”

Named as far back as 300-325 BCE, hematite is derived from the Greek haima, meaning blood. These types of gemstones are found in colors ranging from rust-red, brown, steel-gray to black, it always leaves a red streak when scratched on a scratchpad.

The distinct reddish hue has been used in artwork from the earliest cave paintings. It was a key pigment for Renaissance artists creating paintings with canvas and oil in the Middle Ages. Besides its importance as an ore for iron and in art, it effectively stops radiation making it useful in shielding applications. Plus, it creates a beautiful tumbled stone for those who love to collect them.

Iolite

This beautiful violet-blue stone was the secret to the Vikings’ success in crossing the ocean as they looked through a thin iolite specimen to determine the position of the sun on cloudy days. The key to this unique quality is called pleochroism where different colors are visible at different angles. For example, a piece of iolite may have the classic violet-blue hue on one side, but when it’s turned over, it appears yellow or clear.

A silicate of aluminum, iron and magnesium, iolite (also known as the mineral cordierite) is created in metamorphic and igneous rock formations. Derived from the Greek word ios meaning violet, some iolite is blue enough to look like a sapphire. Some speculate this quality is because of the presence of titanium, although iolites are easily distinguishable because of pleochroism.

This story about types of gemstones appeared in Rock & Gem magazine. Click here to subscribe. Story by Amy Grisak.

The post Types of Gemstones By Letter (A-I) first appeared on Rock & Gem Magazine.

Jasper

Jasper is found throughout the world. This chalcedony is a cryptocrystalline form of silica. Jasper types of gemstones come in colors ranging from green, red, blue, orange, yellow and brown. The colors are because of impurities such as ash, clay or minerals within the stones. Iron typically creates the reddish hues, while manganese oxide is responsible for blues, and inclusions of iron oxide or the mineral goethite create the yellows.

Many times there are types of gemstones with examples of various inclusions, such as with the bloodstone jasper, where chlorite and pyroxene cause the deep green, while iron is responsible for the red speckling. Jasper’s name is based on the French word “jaspre” which came from the Latin “jaspidem” meaning “speckled stone.” This is fitting because when polished, jasper has a speckled pattern seemingly just below the surface.

Kunzite

The best-known variety of spodumene, kunzite is the pink to purple version of this important mineral that is still sometimes mined for lithium production. Kunzite boasts beautiful pink or purplish hues because of the presence of manganese, while chromium creates the greens of another variety, hiddenite.

A fascinating aspect of kunzite is its pleochroic attributes where it displays different colors, such as a combination of pink, purple and transparent, depending on which way you look through the crystal. This is a key consideration when cutting the gem. It also has phosphorescence, which allows the stone to absorb light and then release it in the dark, as with any of our favorite glow-in-the-dark items. The drawback is excessive exposure to sunlight fades its beautiful colors.

With a Mohs rating of 7, eye-catching colors, and the unique characteristics of pleochroism and phosphorescence, it’s even more intriguing to know that large crystals are possible with the best example being an 880-carat heart-shaped kunzite housed at the Smithsonian.

Lapis Lazuli

The beautiful deep blue lapis lazuli is an example of when a gemstone is not a mineral. Instead, lapis lazuli is a rock consisting of multiple minerals, including lazurite, calcite, pyrite, afghanite and several others.

To be considered true lapis lazuli, the rock has to contain at least 25 percent of the mineral lazurite that lends to the distinct blue coloration. Calcite is usually the next most prevalent mineral which often shows up as white layers or mottling. Pyrite provides the shiny gold flecks in some specimens.

Afghanistan is the hotbed of lapis lazuli. There are records of it being mined in the Badakhshan Province of the northeastern part of the country as early as 7000 B.C. The name is derived from the Arabic word “lazaward” meaning “heaven” along with the Persian term for blue, “lazhuward.” In ancient times, Egyptian women also used powdered lapis as an eye shadow. And even in the 1800s, powdered lapis was used to create ultramarine blue paint used in oil canvas paintings, such as Vincent Van Gogh’s “The Starry Night.”

Malachite

A vibrant green gemstone with distinct parallel banding, malachite is a striking specimen and its popularity for thousands of years is no surprise. Derived from the Greek word meaning “mallows,” this correlates to the deep green of malachite with the color of the mallow plant’s leaves.

The gem color is derived from the copper carbonate hydroxide minerals often found in regions near copper deposits. Because malachite is a fairly malleable oxidized copper ore, it’s possible to extract copper from it using sulfuric acid.

The Egyptians also figured out how to remove the copper by placing powdered malachite in a hot fire, which resulted in tiny spheres of copper as a by-product. They used this copper to make cookware, and razors and eventually created stronger bronze by adding arsenic or tin. They also used finely ground gemstones as a distinctive eye paint. Besides adorning the appearance of ancient Egyptians, malachite is one of the oldest known pigments and was identified in the artwork of Egyptian tombs.

Natrolite

Typically found with slender, needle-like crystals protruding from the crystal, natrolite is an eye-catching specimen. It’s difficult to imagine such a fragile-looking stone cut and polished into impressively faceted gems, although high-quality gems are truly rare. Not surprisingly, it’s sometimes called needle stone.

Natrolite leans toward a colorless appearance but can be found in white, light yellow, green, orange, pink, brown or gray. When it’s placed under either longwave or shortwave ultraviolet light, it glows in yellow, orange and sometimes pale green.

A member of the zeolite group, which are hydrated aluminosilicate minerals, the name comes from the Greek words for soda and stone, “natron” and “lithos.” It was officially named by the German chemist Martin Heinrich Klaproth in the early 1800s. Natrolite is found in regions where there are veins of basaltic rocks, along with granite and the igneous rock, gneiss.

Onyx

While onyx and agate are both types of chalcedonies and share many similarities, one way to tell them apart is to look at their banding. Agate sports curved bands and onyx has straight, parallel banding. When many people envision onyx, they think of a black gem but is often found in red, brown or yellow, which is called sardonyx. Red and white layers are usually what is referred to as carnelian onyx, while Nicolo onyx has light blue layers alternating with black.

Since ancient times, artists have created intricately carved cameos. Black onyx grew in popularity during the Victorian Era when mourning jewelry was an integral part of society. After Queen Victoria’s husband Prince Albert passed away in 1861, she and all of the British Empire descended into mourning. Besides onyx, jet, vulcanite and even black enamel were used in the adornments. Many included personal mementos, such as hair, woven into the locket or watch fob.

Peridot

Peridot is the gem variety of the common mineral olivine and one with a unique origination story. Unlike many other minerals that form on the Earth’s surface, peridots are birthed either deep within the Earth’s upper mantle where they are brought to the surface through volcanic activity, or deposited by meteorites.

Because of this relationship with volcanoes, Hawaiian legend claims that peridot symbolizes the tears of Pele, the goddess of volcanoes and fire. It is so intertwined that there are several beaches on the island of Oahu that are made up of green sand that glitters with these tiny green crystals. Its distinct coloration is because of the percentage of iron in the formation of the crystals, yet can vary to the point where the stone looks more yellow, olive or even greenish-brown.

The ancient Egyptians referred to peridots as the “gem of the sun,” and some experts surmise that Cleopatra’s famed emeralds may have actually been peridot gemstones.

Quartz

Quartz might not only be one of the most abundant minerals found on Earth, but it is also possibly one of the most useful as it is found in everything from glass to electronics, and has been critical in the mining industry. One fascinating aspect of quartz crystals is their vibrational ability.

As a piezoelectric material, quartz creates an electrical charge when it’s squeezed. As a result, it vibrates 32,768 times per second, and for nearly a century, quartz crystals have been used in watches, computers, GPS units and a remarkable number of everyday items. Found in several varieties, types of gemstones include rosy quartz, smoky quartz and amethyst, quartz is as diverse as it is beautiful. The coloration differences are often due to natural radiation reacting with specific minerals within the quartz. For instance, iron is responsible for the purple hue of amethyst while aluminum creates the gray of the smoky quartz.

Ruby

The terms “ruby” and “red” are practically synonymous, or at the very least, ruby is often used as an adjective to describe types of gemstones with a particular shade of color. Its name comes from the Latin word for red, “ruber.” Bringing the highest per-carat price of any of the colored stones in the modern market, rubies shine among the corundums, which also include sapphires. Like sapphires, they score high on the Mohs scale ranking just below a diamond.

Pure corundums are colorless, but chromium causes the striking red coloration of rubies. The deeper the color, the more chromium is present. This element also causes rubies to glow under ultraviolet light. Because of rubies’ chemical composition, the first working laser, called the ruby laser, was created in 1960 by Theodore Maiman. One of its first uses was in range-finding equipment, but the technology is used to this day as a light source for medical procedures or high-speed photography.

As this list demonstrates, types of gemstones go well beyond only beautiful objects. The myriad of important day-to-day applications for gemstones gives us a deeper appreciation of what might be considered common gems.

This story about types of gemstones by letter appeared in Rock & Gem magazine. Click here to subscribe. Story by Amy Grisak.

The post Types of Gemstones by Letter (J-R) first appeared on Rock & Gem Magazine.

The Start

In 1935, a Depression-era government works program allowed the Milwaukee Public Museum (MPM) to continue operations and provide much-needed jobs to local unemployed workers. These new employees spent their days preparing the Museum’s Earth Sciences displays. In the evenings, they held meetings in their homes to learn more about the rocks, minerals, and fossils.

With the MPM offering use of its Trustee Room for meetings and the Milwaukee Journal providing publicity, the non-profit Wisconsin Geological Society was formed in early 1936.

Branching Out

The newly-found box revealed how active the WGS was in building a solid foundation for its club and also for clubs across the country to connect. For instance, in 1940, the WGS was one of three clubs involved in the creation of the Midwest Federation of Mineralogical and Geological Societies (MWF). In 1950, WGS members were among the eight delegates to the first American Federation of Mineralogical Societies (AFMS) meeting held in Salt Lake City.

In 1984, the Wisconsin Geological Society hosted a large joint rock and mineral show with the MWF at State Fair Park in West Allis that resulted in a 36-page document outlining all the activities including field trips. Joint shows were previously held in 1941, 1944, and 1954.

Blackjack Bonanza

Corn dogs, cotton candy, amusement rides, and a lead/zinc mine tour? Yes!

From 1963 to 1966, Blackjack Bonanza mine tours were a re-creation of a real lead/zinc mine at the Wisconsin State Fair. It was a 15,000-square-foot exhibit that sported a 65-foot headframe tower, an elevator shaft that shook to simulate the ride down into the mine tunnel, and a 30 by-45-foot processing room. A hidden 50-ton A/C unit cooled the mine tunnel making guests think they were far below ground. Mine tours cost fairgoers 75 cents per adult and 24 cents per child.

Like other fair attractions, the Blackjack Bonanza became a part of history as well as the role the WGS played in its existence.

The box revealed that in 1966, members of the WGS took over the 10-day, 12-hour per day, operation of the Blackjack Bonanza mine tours. Club members provided ticket sales, tour guides, and mine workers. They also provided mineral samples for a museum display as well as staff to operate the gift shop.

Naming the Wisconsin State Fossil

State fossils are nothing new. Lots of states have them. But through the box and personal interviews, WGS members found out that club members played a significant role in the process for their state. It took three attempts before the trilobite (Calymene celebra) was officially named Wisconsin’s State Fossil in 1986.

The first attempt was made in 1981 by a UWM geology student, Mark Shurilla, but he neglected to name a specific species of trilobite. The bill failed.

Wisconsin Geological Society members picked up the process in 1983, narrowing the field to the Calymene celebra, found primarily and prolifically in Wisconsin. Again, the bill was defeated.

In 1985, at the direction of the WGS Board of Directors, club president, and chief lobbyist for the bill, Margaret Pearson, made a final and successful attempt. This time, the bill was sponsored by State Assembly member, Jeannette Bell, daughter of WGS members Harold and Luella Jeske. Members of WGS were present at the bill signing on April 2, 1986, in Madison, Wisconsin, as Margaret presented Governor Anthony Earl with a trilobite specimen to mark the occasion.

More Fossils

The original Milwaukee Public Museum opened its doors to the public in 1898. It now houses the Milwaukee Public Library. The board room where the first official WGS meeting was held still exists and is on the National Register of Historic Places.

In 1975, the Museum moved to a new facility across the street but did not have enough room for all of the geology exhibits, including fossils that WGS members originally displayed in 1936.

Fundraising is underway for a new facility with a groundbreaking scheduled for late 2023. It should be open to the public sometime in 2026. It will be a representation of ancient sea stack formations present in Wisconsin’s Mill Bluff State Park. The rounded edges of that building will showcase the glacial weathering that formed Wisconsin and deposited those fossils. Inside, will be displayed those original WGS fossils from 1936.

Plan, Collect, Verify & Store

While the plastic box brought history to life for WGS members, they soon found out its information was incomplete and that members had bits and pieces of history in lots of places; old newsletters here, photo books there. Records ended up in various places as officers and leadership transitioned over time. The club historian, and volunteers, made a plan to gather all of the documents. Here is a to-do list for other club historians that may have the same circumstances.

• Scan and identify all photos and documents and create a digital file

• Contact club officers, new and old, for any information in their possession

• Contact outside sources to verify and provide additional information

• Create documents and a presentation to share with members

• Develop a storage plan to preserve past, current, and future records

After collecting information from members, the first critical step for the WGS was to scan and identify photos and documents and place them in a digital file, backed up on a memory stick.

Finding More Photos

Next, was to contact club officers and members to see if any files or pictures had been handed down to them. Also, an article was published in the club’s monthly newsletter, The Trilobite, asking members who are no longer able to attend meetings to offer any information or photos.

Early on, Wisconsin Geological Society members took field trips, attended study groups, participated in mineral shows, and enjoyed parties and picnics just like they do today. One of the early members must have been an avid photographer as many of these functions were captured with lovely photos. The documentation and preservation of those photos were poor. Names of members and photo locations were often missing or destroyed the photograph by writing or gluing a note directly on the photo.

An Interesting Photo

One of the most interesting photos in the collection was of young boys, wearing knickers, admiring the rocks and minerals in a Wisconsin Geological Society display case. The photo had a typewritten note paper-clipped to it, “Hobby Show November 24-27, 1950?” A scanned copy of this photo was emailed to the Milwaukee Public Library (MPL) archives department for verification. They were able to confirm that a hobby show was held from November 24 to 27 in 1949, however, they could not verify that this photo was taken at that show. According to historical fashion records, knickers for young men had gone out of fashion in the late 1930s.

Photo identification is important. Always record the following information:

• Event

• Place/location

• Date taken

• People, use an easy format of left to right (L to R) and rows top to bottom

• Photographer, if possible

Community Help

Research to fill in the missing information became the next priority. Organizations whose history crossed the club’s path came first. Historical societies and newspaper articles provided another great resource.

Some sources responded immediately, while others required a longer response time. The most successful recoveries of information resulted from telephone calls which produced a real person contact. Additional details continue to be added to the club’s historical records as a result of these contacts.

Long-Term Storage

After a huge effort to gather all of this history, it became important for the WGS to change how it gathers and stores its data in the future. The Milwaukee Public Library has worked with club members to develop a plan for the WGS to donate its current historical records and future yearly updates. Current and future WGS members will retain access to all of their records during normal library business hours.

This story about the Wisconsin Geological Society’s history appeared in Rock & Gem magazine. Click here to subscribe. Story by Sue Eyre.

The post Wisconsin Geological Society History first appeared on Rock & Gem Magazine.

“It is amazing that this small (25 miles long by 10 miles wide) batholith of the Spruce Pine Mining District lying in Mitchell, Avery and Yancey Counties is a world-class mineral deposit, and so important an ingredient to making the products we use daily,” says Alex Glover, whose 45-year career in the mining industry reflects a rock-solid list of geological credentials. “We often take for granted the role minerals play in the quality of life we enjoy today.”

Modern-Day Minerals

The U.S. Geological Survey describes a batholith as a type of igneous rock that forms when magma rises into the earth’s crust but does not erupt onto the surface. But the Spruce Pine, NC, Mining District isn’t just any old mass of cooled magma. The 380-million-year-old feldspar, mica and quartz deposits found in these three neighboring counties run most of our modern-day conveniences.

“Almost everyone uses products every day derived from the Spruce Pine Mining District,” Alex says. “Even more amazing is how it took colliding continents and millions of years to place this valuable resource in western North Carolina.”

“If you came to Mitchell County you wouldn’t have a clue as to the importance of this area to the entire world,” says Mandi Polly, who worked in quartz operations for 21 years before her role as executive director with the Mitchell County Chamber of Commerce.

“Think what would happen if the world couldn’t produce computer chips! This district supplies the production of fiber optic cable, solar components and many products in our daily lives. I honestly don’t think,” she grins, “that the majority of people in this area even realize the significance of our mines!”

Mineral City From the Ground Up

“Spruce Pine, NC, has mining deep in its roots and is known as The Mineral City,” she says. In addition to historic old mines like the Hoot Owl, the region has gem mines and the Mineral Museum of North Carolina. It is host to the NC Mineral and Gem Festival (now in its 64th year) and the 36th annual Grassy Creek Mineral and Gem Show.

A neat local side note she adds is how Spruce Pine Quartz supplies the sand for the Masters Golf Tournament, “because it’s so white and pristine.”

Early Mining Fame

Some of the oldest original mines — the Clarissa, Ray and Sinkhole — are believed to have been resourced hundreds of years earlier by First Nations in search of decorative mica for ceremonial events and, after Massachusetts Bay Colony recognized wampum as currency in 1650, for monetary exchange.

Alex says local lore recounts how word of North American mica mining by Native Peoples drew Hernando DeSoto to Spruce Pine in the 1540s, in search of mineral wealth he presumed would be gold and silver. But the only “silver” DeSoto found was Muscovite mica.

Wedgewood & Spruce Pine, NC

Two centuries later and an ocean away, English ceramics maker Josiah Wedgewood heard about feldspar and kaolin being mined by the Cherokee, from pegmatite deposits in what would become Macon County. The softer (Mohs 6) feldspar, in opaque shades of white to gray to rose, easily broke along flat faces (in a process known as cleavage) in comparison to irregular, curved breaks created by the conchoidal fractures of harder (Mohs 7) quartz.

Wedgewood had five tons of this “Indian clay” shipped to Staffordshire to use in the creamcolored earthenware that so entranced King George III’s wife, Queen Charlotte, that Wedgewood was granted permission to style himself, “Potter to Her Majesty” and call his fine pieces, Queen’s Ware. The feldspar clay had come from what would be incorporated in 1855 as Franklin, North Carolina. It was dubbed the Gem Capital of the World after discoveries like the 64.83-carat Carolina Emperor, the largest emerald ever found (2010) in North America.

Rubies & Sapphires

Baltimore gem prospector William E. Dibbell was a century ahead of his good instincts when it came to the rubies and sapphires the region would one day prove to yield but, at the turn of the 20th century, he did see untapped potential in the residual feldspar being discarded by mica mines like Flat Rock.

So did the Golding Sons ceramic plant in East Liverpool (Ohio), who liked Dibbell’s ceramic-grade feldspar so much that they wanted more, leading to the creation of the Carolina Minerals Company of Penland and the opening of the Deer Park Mine to satisfy the appetites of ceramic plants in Trenton, Wilmington and Liverpool.

The 1940s were a game-changer. Until then most of the work, especially the ore separation of minerals (feldspar, mica, quartz) was done by hand or crude machinery. Between 1944 and 1949, a chemical separation process jointly developed by feldspar mining companies, the Tennessee Valley Authority and North Carolina State University Minerals Research Laboratory, led to a high-capacity process still used today known as ‘Froth Flotation,’ that separates feldspar and quartz as well as mica and iron (mostly garnet) from rock and ore.

Not-So-Hidden Gems – Feldspar

“Modern-day mining methods, research, plant production, safety, and product development have enabled the extraction and use of these high-purity mineral resources from the earth to enhance our quality of life,” says Alex.

It’s that extraordinary purity that makes the natural treasures from Spruce Pine, NC, so valuable.

Feldspar makes up roughly 65% of the igneous pegmatite in Spruce Pine, NC, and is an important source of aluminum, potassium, and sodium for making glass – from windshields and computer screens to baby bottles and light bulbs.

“Feldspar is the most abundant mineral on the earth’s surface and crust, but its purity as an ore is rare,” he says.

Spruce Pine, NC, feldspar has come a long way from Wedgewood ceramic teacups. Today, feldspar serves as a flux to fuse or melt other ceramic ingredients at a lower temperature, cementing the crystalline phases of other ingredients together while imparting improved strength and durability. “Its special qualities allow ceramic manufacture of pottery, plumbing fixtures, electrical insulators, tile, dinnerware, planters, and structural ceramics to name a few.”

Mica in Spruce Pine, NC

If feldspar composes 65% of the local pegmatite, mica accounts for another 10% of deposits. Originally used in heat-resistant glass for wood and coal stoves (isinglass), and insulating World War I and II radio tubes, the same properties are used today as a reinforcing plastics and oil well drilling fluid additive, in specialty component electrical insulation, metallic flake automobile paint and cosmetics.

The flat particle shape of the silver-to-white variety called muscovite mica lends itself to drywall joint compound and sheetrock joint cement.

“Muscovite’s flat particle shape and light color allow it to serve as an anti-shrinking agent,” Alex explains. “It applies as a smooth, damp putty, but because of mica’s flat particle shape, it interlocks the mud as it dries, thus reinforcing a filled area without shrinkage and also serving as a fire retardant within drywall joints.”

In the early years of production, the quartz composing 25% of this pegmatite was treated as discarded waste but now it is the most valuable component of the region’s three major minerals. “Froth Flotation enabled better separation of the three minerals, especially the quartz,” he says, thus ensuring that Spruce Pine Quartz ranks among the most important strategic minerals in the world today. Its lower-purity quartz is used as industrial white sand and valued for use on such fine golf courses as Augusta National Course in Georgia, host of the Masters Tournament. More recently, it has been incorporated into the development of quartz countertops for the home.

Down to the Roots

“It’s important to know that even before computers were a concept, mining was a very important part of Mitchell County’s economy and history,” says Mandi. “The quartz business helped my family as I was growing up. My husband’s work in rocks and sand supports our family. My son-in-law works in the quartz business. So it is definitely supporting future generations!

“As of 2022, according to the NC Department of Commerce, mining corporations are the second-twelfth-largest employers in Mitchell County. The mining companies are not only crucial for supplying many jobs but are also very active in the communities. Many serve on boards, help with local schools, sponsor sports teams and host events, support nonprofits, and give back, through volunteer hours and countless other projects.

“This is where I choose to stay and raise my children and grandchildren. We truly are – all pun intended — a hidden gem. Spruce Pine, NC, hasn’t been called The Mineral City by chance. Because that is who we are, down to our roots.”

This story about the Spruce Pine, NC, mining district previously appeared in Rock & Gem magazine. Click here to subscribe. Story by L.A. Sokolowski.

The post The Spruce Pine, NC Mining District first appeared on Rock & Gem Magazine.

Identifying the Risks of Radioactive Minerals

Understanding which parts of your collection may pose a risk is the first step. You might have just a few individual, radioactive mineral specimens. But some large rocks may also contain an amalgamation of multiple types of potentially radioactive minerals. In addition to these radioactive minerals, there are also daughter products that are created as the result of radioactive decay. Daughter products, such as radium, radon gas and uranium, are themselves radioactive.

According to Alysson Rowan, author of Here Be Dragons or The Care and Feeding of Radioactive Mineral Species, some radioactive minerals may even be hiding in plain sight. “A specimen that doesn’t look very good because it’s not well crystalized — somebody may cut that into a decorative stone and mount it for wearing,” Rowan says. “You can find these things on sale, and there’s no mention of the fact that it is radioactive.”

Based in Holsworthy, England, Rowan is also a former radiation safety worker with extensive training in geology. She continues, “There’s no mention that this is not something that you would want to wear, so, people buy these things and wear them in ignorance.”

Detection Equipment

Because uranium minerals tend to be very colorful, they’re among the most popular with collectors. “The other thing is that there are a lot of them that are fluorescent,” Rowan says. “With uranium minerals, you tend to get greens and yellows, but there are minerals that glow blue, and red, and I think there’s even one that’s now known to fluoresce purple.”

Incidentally, to test the radioactivity of your stash, you’ll want to purchase a handheld radiation detector. “If they’re going somewhere to collect uranium minerals or they expect to find uranium minerals, a handheld ‘Geiger counter’ is a must-have,” Rowan suggests. “Of course, they’re not all Geiger counters now. . . . A lot of them are scintillators which are a lot more sensitive and a lot more durable. They generally show how much radiation they’re detecting either on a meter or on an alphanumeric display.”

You can also find used Geiger counters for sale online. “A lot of people buy them second-hand on eBay,” she says. “The American Civil Defense monitors are very, very popular because there’s a lot of them about.”

Saléeite and autunite are two colorful — and radioactive — minerals. “In bright sunlight, you can see the fluorescence,” Rowan notes. Both are in the bright yellow-green range.

Just don’t get too attached to that autunite, as it will literally disintegrate. “Autunite is what’s known as a metamict,” Rowan explains. “It decays radioactively, and the radiation damages the crystal. Inside a few years, it’s just a pile of dust. . . . And, so, autunite will actually spread all over the place.”

Radiation Effects

Containing that radioactive spread is paramount because the negative effects of radiation on the body are cumulative. In other words? The radiation you absorb builds up over time. You can inadvertently expose yourself to radiation internally by absorbing contaminants through your skin. You can also inhale or ingest radioactive contaminants.

The acute effects of radiation exposure can range from erythema — akin to a deep tissue sunburn — to renal failure. “The uranyl minerals—that is uranium oxide as a radical—are toxic to your kidneys,” Rowan says. “So, that is what you’ve got when you pick up most fluorescent minerals. It’s uranyl phosphates, uranyl nitrates—they are highly toxic.”

Over the long term, exposure to some radioactive compounds can even result in bone cancer and leukemia. In her book, Rowan writes, “Inhaled uranous and thorium compounds, and to a lesser extent the uranyl compounds will result in both toxic and radiation damage to the lung. Long-term effects will include bronchitic and emphysema-like symptoms as well as a range of pulmonary and pleural cancers.”

Smoke Alarm

Keeping cigarettes, incense, and other smoky stuff away from radioactive specimens is especially important.

For safety’s sake, you should never eat or drink while handling radioactive minerals. Applying a quick smidge of lip balm’s another no-no. And smoking is right out, too.

“The thing about smoking is one thing that you do is that you handle the rock and you put your cigarette to your mouth and you’ve immediately got rock dust on your lips,” says Alysson Rowan, the author of Here Be Dragons or The Care and Feeding of Radioactive Mineral Species.

What’s more, let’s say some of your specimens contain uranium. As uranium goes through its multiple stages of decay, it eventually releases radioactive radon daughter products and radon gas. “The airborne activity from radon daughters and radon gas itself will attach themselves to smoke,” Rowan continues. “So, when you re-inhale smoke, you’re inhaling the radioactive contaminants in the atmosphere.”

In her work, Rowan writes, “It has been noted that the presence of blue smoke from cigarettes (the plume that rises from the burning tobacco) collects the radioactive radon daughter products more surely than any other means of concentration. This means that the spent smoke you breathe in a high radon concentration area is bringing those radioactive materials into your lungs in a form which tends to remain inside your body.” Such radiation exposure in the human body is cumulative. Rather than dissipate, the radiation exposure adds up. “The consensus of scientific opinion is that a given dose from radon is possibly 10 or 15 times as dangerous to a smoker as to a nonsmoker,” Rowan notes. To mitigate this risk, never smoke in areas where you keep radioactive specimens.

Minimizing Exposure

Although different minerals pose differing degrees of risk, if you are pregnant, you should avoid contact with radioactive minerals altogether. As for young children? “Before puberty, we are a lot more susceptible to radiation damage because of the rapid cell division,” Rowan says. “Children should not be around. . . radioactive minerals more than absolutely necessary for their study.”

There are several precautions you can take to minimize your overall radiation exposure and still appreciate the radioactive specimens in your collection. Besides the degree to which a mineral is radioactive, the amount of the mineral in question matters as well as the cumulative amount of time that you spend in direct contact with it.

“If you sit with a pound of uraninite using it as a paperweight on your desk, that is going to give you a problem eventually,” Rowan maintains. “If, on the other hand, you have that pound of uraninite and it’s in a lead-acrylic case, that reduces the dose rate and, therefore, it’s not quite the same problem.”

Display Do’s and Don’ts

“You also have to take into account how far you are from that specimen,” Rowan adds.

When you increase the distance between yourself and the specimen, you decrease your potential radiation dose. Adding shielding materials like lead, wood or glass can further reduce your radiation exposure.

“For the most part, you put [your collection] on display in a cabinet,” she says. “The idea is that you’re keeping dust off of your specimens, but you’re keeping dust from the specimens fixed.”

Regarding those uranium-rich minerals, keep in mind that uranium decays into radium which, in turn, will decay into radon gas. Because this heavy, radioactive gas can easily migrate, you should air out your uranium mineral display cases periodically. “I’ve done this with my own cabinet,” Rowan says. “You open the cabinet and stick your [radiation] meter in and the radiation count goes up. And, over about half an hour, the count rate goes right down, because the radon daughters in there only have a short half-life.”

Still, she cautions, “If you’re a serious uranium collector, then it’s probably a good idea to have vented cabinets—venting to the outside world.”

Also, never store or display uranium minerals in a basement. “Radon gas is an awful lot denser than air,” Rowan explains. “It’s a big atom and it will hang around for a couple of weeks.”

Handling How-To’s

If you do need to handle a radioactive mineral specimen, don’t dally. “If you’re working with it for too long, that’s all additional exposure,” Rowan says. “So, the amount of time that you’re in contact with the rock, you need to minimize it. And you need to make sure that you don’t spread contamination everywhere.”

To that end, she suggests wearing protective clothing and disposable gloves and protecting your work surface with a disposable covering. Washing carefully with soap and water is also key. “If you handle a radioactive rock, you’ve got radioactive rock dust on your fingers and you’ve got to wash it off,” Rowan says.

Finally, to prevent ingestion or inhalation of radioactive contaminants, never eat, drink or smoke when working with radioactive minerals, and, Rowan concludes, “Don’t be paranoid, but do take care.”

This story about radioactive minerals appeared in Rock & Gem magazine. Click here to subscribe. Story by Susan M. Brackney.

The post What are Radioactive Minerals? first appeared on Rock & Gem Magazine.

After 30 years of procrastination, I purchased a brand-new rock saw and grinder/polisher. Wow, did I have fun! For that first few months of cutting and grinding, I was in seventh heaven. All those lovely rocks I had lusted after for so long were finally put under my polishing wheel: lapis, agate, jasper, tiger’s eye, malachite, turquoise, chrysocolla and quartz.

But I soon began to experience a nasty and completely unexpected cavalcade of health problems: coughing, hoarseness, difficulty clearing my throat, breathlessness, and a dull ache in the pit of my lungs. Of course, I had always worn safety glasses with side protection, as recommended in every manual, but a mask seemed a cumbersome hindrance. As the situation worsened, I tried several dust masks, but there was little improvement. It was time to do a little research, so I hit the books and started talking to fellow rockhounds. It was a revelation. Rock dust from lapidary work turns out to be more than just a nuisance; it can be deadly.

Dangerous Dust

A single heavy dose can cause crippling lifelong problems. It attacks the lungs in a variety of ways: First, by coating the inner lining and blocking the transmission of oxygen into the bloodstream. Second, tiny sharp fragments slice and cut into the alveoli, which coat the inner lining of the lungs, causing irritation and inflammation. Fresh dust seems to be more harmful because the sharp edges have not had a chance to be softened by moisture. Some forms of rock dust are quite poisonous in and of themselves. Whether it is inhaled, ingested, or contacted by exposed skin, the effect can be injurious to your health.

Copper Oxide Minerals

Among the worst offenders are minerals containing copper (II) oxide (CuO), the higher oxide of copper, which can cause damage to the endocrine and central nervous systems. These minerals include some of our most colorful and treasured semiprecious stones: turquoise (9.8% copper oxide), chrysocolla (45%), and malachite and azurite (70%). These percentages are only close approximations; each rock has its own signature of impurities.

It is worth remembering that other closely related copper compounds are highly bioactive and have been used in pesticides, fungicides, and wood preservatives for decades. This is dangerous material. These high-copper rocks should not be licked to bring out the color, and oil mixed with the dust should be carefully cleaned off exposed skin.

Several lapidaries who smoke have described their own novel test for overexposure: Apparently, copper-impregnated dust combines with nicotine and tobacco tar in saliva to form a sickeningly sweet compound similar to saccharin. When their mouths start to taste like a candy factory, these rockhounds know it’s time to quit. Another sign is influenza-type symptoms. Symptoms of CuO dust poisoning mimic the flu, causing headaches, coughing, sweating, sore throat, nausea and fever. Skin, eye, and respiratory tract irritation are also common, along with a distinct “metallic” taste. A common name for these health effects is “metal fume fever.”

Silicate Minerals

Almost all the rocks most favored by cutters and polishers contain compounds that can be dangerous when inhaled. Silicates are the most common family of minerals on Earth, and silicosis has long been one of the chief hazards facing stonemasons.

The ancient Greeks and Romans were the first to observe its ravages and correctly associated the problem with mining and rockwork. Similar to the “black lung disease” of coal miners, it came to be known in later years as “grinder’s consumption.” The simple steps taken to prevent it were a major achievement in the modern field of occupational health. Ironically, although silicosis is well understood today, thousands still die from its effects every year, mainly from mining and sandblasting in the third world.

The symptoms of inhaling crystalline silica (SiO) dust include shortness of breath, cough, fever, emphysema, pulmonary fibrosis, lung scarring, and increased susceptibility to tuberculosis and cancer. Silicosis often takes many years to develop from repeated exposure to low doses of dust, but once established it is irreversible.

Widespread Silicates

The silicates include a bewildering variety of precious and semiprecious stones. In fact, it’s hard to imagine the world without them, as they can be found in every class of rock and occupy a niche in every conceivable geological environment on the planet.

The family includes quartz, chalcedony, jasper, agate, aventurine, bloodstone, carnelian, chrysoprase, amethyst, opal, onyx, beryl, petrified wood, obsidian, flint, chert, soapstone, sandstone, glass and tiger’s eye. In almost all of these, the content of silicon dioxide approaches or exceeds 50%.

It should be mentioned that African tiger’s eye also exposes the lapidary to another potent danger: asbestos. The vibrant optical effect of its chatoyancy is caused by parallel-oriented, finely fibrous amphibole asbestos. Serpentine has a high chrysotile asbestos content, but this is not considered quite as dangerous as the tiger’s eye. Some soapstone varieties also contain asbestos and should be cut or carved with caution.

Fossil Dangers

Radioactivity from fossils is a hazard that isn’t often top of mind. In a recent study of 300 randomly selected fossils from the Hagerman Fossil Beds of Idaho conducted by C. Neal Farmer, Ronald L. Kathren, and Craig Christensen, a handheld Geiger-Müller survey instrument detected discernible levels of radiation one to two orders of magnitude above the ambient level of background radiation in three-quarters of the specimens (“Radioactivity in Fossils at the Hagerman Fossil Beds National Monument”, Journal of Environmental Radioactivity, Vol. 99, Issue #8, August 2008, pp. 1355-1359). That is a huge difference.

In some areas, like the Hagerman Fossil Beds National Monument (Idaho) and the Morrison Formation at Dinosaur National Park (Colorado/Utah), fossils have even been hunted using Geiger counters.

According to the study, radioactive fossils seem to occur most commonly between 900 and 1,000 meters above sea level in ancient sandy riverbeds, while clay-rich deposits and those at other altitudes do not seem to show these high levels. Apparently, naturally occurring uranium produces radium, which decays into radon, an inert gas. Ancient groundwater transported these radioactive elements into sandy fossil-bearing areas, where they precipitated out of solution during the fossilization process. Even small fossils like shark teeth and trilobites can have significant readings.

The National Park Service is so concerned that it put out a “Conserve O Gram” with detailed instructions for handling and displaying specimens. While it is probably safe to collect most fossils, at the very least, you should wash up and change your clothes after leaving the field. And always wear a respirator when you cut or polish the pieces—radioactive dust is highly carcinogenic!

Tips for Safe Handling

But enough of the doom and gloom. A few simple precautions can almost completely eliminate the threat of injury from most rock dusts. Here is a list of suggestions that will make your workshop a lot safer and allow you to enjoy lapidary work in good health.

1. Wear a Mask

Always wear a National Institute for Occupational Safety and Health (NIOSH) approved respirator with replaceable cartridges and dust filters. Some cartridges today combine a prefilter with the cartridge, which makes things simpler.

Respirators provide a wide variety of protection against dusts, solvents, fumes and mists. They are designated N, R and P, depending on the cartridge’s ability to filter out oil; N stands for “no protection”, R for “resistant to oil”, and P for “oil-proof”. The number that follows the initial tells you what percentage of the particulates is filtered out by the cloth prefilter. For example, an N-95 respirator will not keep out oil spray but will screen out 95% of airborne dust particles.

Avoid cheap dust masks; they don’t fit tightly enough and they filter poorly. If you can, try on several different respirators at the store to get the best fit. Shave your beard, if you have one, to get an airtight seal. Store the mask in a closed container or plastic bag when it’s not in use, and occasionally wash it with warm soap and water, both inside and out.
Try this simple negative pressure test on your respirator: Block up the air inlets, breathe in, and hold your breath for 20 seconds. If the mask is still held airtight against your face, it fits. Cartridges should be changed after about eight hours of use.

2. Work Outside and/or Ventilate

An open window or air conditioner does not provide adequate ventilation for the lapidary workplace. The simplest solution is to work outside. This keeps most contaminants out of your workshop and costs nothing, but it is not always possible.

If inside is your preference, consider setting up a local exhaust ventilation system. This would include a dust hood to collect contaminants, ducts to carry them outside, and a suction fan to power the system. Adjustable blast gates would allow a dust hood to be placed next to each appliance. Ducts should be circular, with as few bends as possible, and should exit the shop. If you have close neighbors or are processing a lot of rock, provide a dust collector to remove contaminants from the vented air.

Setting up such an elaborate system can be expensive and time-consuming for the part-time hobbyist. Some woodworking tool suppliers have come up with an ingenious alternative. They have adapted a wet/dry-type vacuum cleaner with a High-Efficiency Particulate Absorbing or Arresting (HEPA) filter to collect shop dust using a little extra pipe and some suction nozzles. There is no reason this system should not work for rock dust, as well. The vacuum should be placed outside the house because the dust-laden air sucked into the intake will be blown out the vacuum’s exhaust port. Even HEPA filters fail or become clogged, and some dust will always slip through. It’s far better for it to be blasted outside than into the shop or another enclosed area. Kits, diagrams, pipe and suction nozzles are available on the internet. Search for “dust collection” and “dust collection network”.

3. Lubricate

Always use water or oil as a lubricant when cutting, drilling, polishing or faceting, but be aware there are problems with both fluids. When water evaporates, it stops holding the dust down, allowing it to become airborne. A fine oil mist laden with toxic dust can be kept out your lungs with a good respirator, but it will settle on skin surfaces and stick like glue. Also, most lapidary oils are highly irritating or downright poisonous to breathe. Some, like old-fashioned kerosene, are dangerously flammable, as well. Everyone has their favorite method, but I work outside using mineral oil and a P (oil-proof) respirator cartridge with a built-in 100% particulate filter.

4. Cover Up

Always wear a head covering and apron and/or coveralls when grinding, and change clothes after you have finished. Rock dust loves to stick to clothing and hair, and you will carry it around the house and breathe it all day long (as will your family) if you don’t change. Take a shower after your lapidary work, shampoo your hair and use lots of soap. Launder coveralls and work clothes frequently. Disposable clothing, coveralls, and an apron might also be an option.

5. Don’t Sweep

Never dry sweep the workshop. Most of the dust will just become airborne and migrate elsewhere. Use a vacuum cleaner with a HEPA filter instead. If you really want to get down and dirty, use a wet mop on the floor and a wet rag with a water bucket on other surfaces.

Not all of these suggestions need to be slavishly followed. If you grind infrequently, you can probably forget some of them, but if you are an addict like me, you might want to implement most. Individuals vary greatly in their tolerance to rock dust. Some will go through life with nary a problem, but others can be extremely sensitive. Low doses on a daily basis will slowly accumulate, and that dust isn’t going anywhere once you breathe it in. Smoking and living with a woodstove or in an area with poor air quality will make you that much more vulnerable to problems. Listen to your body. If your lungs start to complain, take more precautions; you only have one set to last a lifetime.

FURTHER READING: Health Hazards Manual for Artists, 6th Ed., by Michael McCann Ph.D. and Angela Babin (Lyons & Burford Publishers, 2008)

This story about how to handle lapidary minerals safely previously appeared in Rock & Gem magazine. Click here to subscribe. Story and photos by Douglas Hamilton.

The post 5 Tips to Handle Lapidary Minerals Safely first appeared on Rock & Gem Magazine.