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.

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.

A few prospectors did indeed make their fortunes. Still, most received their reward by participating in an adventure that thrilled the nation and introduced words and terms like “radioactivity,” “Geiger counter,” and “radiometric prospecting” into the general vocabulary.

Although finding a million-dollar uranium deposit today is unlikely, understanding radioactivity and knowing how to detect it can greatly enhance the mineral-collecting experience. Radioactivity is one of the fascinating physical properties of minerals. It is ionizing energy in the form of particles and rays produced by the spontaneous disintegration or “decay” of unstable atomic nuclei.

Understanding & Identifying Radioactivity

While this definition might seem a bit intimidating, getting a practical handle on radioactivity is not that difficult. Admittedly, the word is loaded with negative connotations linked to nuclear weapons, fallout, toxic waste disposal, reactor meltdowns, and the hazards of radon gas. Nevertheless, radioactivity is very much a part of the natural world, especially the world of mineralogy.

Minerals are described as radioactive when they emit energy in the forms of alpha, beta, or gamma radiation. “Radiation” is the catchall term for energy in the form of waves or particles. Gamma rays make up the extreme high-frequency, shortwave end of the electromagnetic spectrum, broadband of radiation energy that includes radio waves, microwaves, infrared, visible light, ultraviolet, and X-rays.

Alpha and beta particles are not forms of electromagnetic energy. Alpha radiation refers to positively charged, high-energy, low-mass particles that consist of two neutrons and two protons (the nuclei of helium atoms). Beta particles can be negative or positive; negatively charged beta particles are high-speed electrons, while positively charged beta particles are positrons (the “antimatter” counterparts of electrons).

Exploring Ionization

Alpha particles, beta particles, and gamma rays (along with X-rays) are classified as “ionizing” radiation, meaning that they have sufficient energy to ionize atoms in the materials they strike. Atoms become ionized when they lose electrons and assume a net positive charge. Because it disrupts normal biochemical functions on the molecular and atomic levels, ionizing radiation can be harmful to living tissue. Ionizing radiation is produced by nuclear fusion, nuclear fission, and atomic decay, the latter being the natural disintegration of the nuclei of unstable, heavy elements or isotopes (elements with different numbers of neutrons).

Ionizing radiation can be cosmic, man-made, or geophysical in origin. The sun, a giant nuclear fusion furnace that emits intense gamma radiation, provides most of our cosmic radiation. Fortunately, very little reaches the Earth’s surface because of its distance from the sun and atmospheric absorption. During the past 80 years, the Earth’s cumulative environmental radiation load has increased significantly due to uranium mining and processing, nuclear weapons manufacture and resting, nuclear power and X-ray generation, accidental radiation releases, production of radioactive isotopes for medical and industrial uses, and radioactive waste disposal.

Geophysical Radiation

Mineral collectors, rockhounds, and prospectors are most interested in geophysical radiation, which is emitted by natural radioactive elements that are present in minerals as essential or accessory components. Most geophysical radiation is produced by uranium and thorium, which occur in trace amounts in many igneous rocks, especially granite. The effects of geophysical radiation go far beyond surface radioactivity. An estimated 80 percent of the Earth’s internal heat is produced by the atomic disintegration of uranium, thorium, and the elements and isotopes in their atomic-decay chains.

Of the 92 naturally occurring elements, 11 are radioactive. Of these, only uranium and thorium are relatively abundant. Uranium was identified as an element in 1789; it was isolated in 1841 as a very dense, silvery-white metal that oxidizes rapidly in air. Ranking 51st in crustal abundance, uranium is about as common as tin.

Thorium, discovered in 1828, is similar in appearance to uranium but is half as dense and much more common. Until the discovery of radioactivity, uranium and thorium were little more than laboratory curiosities. Small quantities of uranium oxides were used to color glass yellow, while thorium compounds that incandesce (emit visible light) when heated were employed in gas-lantern mantles.

Driven by Discoveries

The discovery of radioactivity followed investigations into the mysterious, penetrating “invisible energy” that was produced by passing an electrical current through vacuum-discharge tubes. In 1895, the German physicist Wilhelm Conrad Röntgen (1845-1923) named this energy “X-rays” to signify its unknown nature. Radioactivity was accidentally discovered in 1896 when French physicist Antoine-Henri Becquerel (1852-1908) studied the effects of X-rays and sunlight on potassium uranyl sulfate, a compound that fluoresced in direct sunlight. Becquerel placed this compound atop photographic plates wrapped in lightproof black paper, then exposed it to sunlight.

He noted that the photographic plates became exposed and attributed this to some type of penetrating energy related to fluorescence.

When cloudy weather delayed his experiments, Becquerel stored both the uranium compound and the unexposed, wrapped photographic plates together inside a dark desk drawer. Later, out of curiosity, he developed the plates and found they had already been exposed. This exposure meant that the uranium compound—without any induced fluorescence—continuously emitted invisible, penetrating rays. Becquerel then demonstrated uranium itself, not its compounds, was continuously emitting these rays, which became known as “uranium rays” or “Becquerel rays.”

Marie Curie & Ernest Rutherford

Among the first to investigate these rays was Marie Curie (1867-1934), the Polish-born French chemist and physicist who coined the term “radioactivity.” In 1898, after extracting uranium and thorium from uraninite (uranium oxide), Curie was surprised to find that the uraninite was still highly radioactive. Concluding that it must contain additional sources of radioactivity, she extracted two previously undiscovered radioactive elements—polonium and radium. The radium was particularly interesting because of its extraordinarily intense radioactivity.

In 1902, British physicist Ernest Rutherford (1871-1937) proposed that radioactivity consists of what we now know as alpha and beta particles, and gamma rays. He found that alpha and beta particles lose their energy relatively quickly as they pass through materials, while gamma rays have a far greater penetrating power. Until the discovery of radioactivity, most scientists believed that the smallest particle of matter was the atom, which was indivisible and unchangeable. But Rutherford challenged the idea of atomic indivisibility by proposing that alpha and beta particles were subatomic components of disintegrating atoms. This concept opened the door to modern particle physics and an entirely new understanding of the nature of matter and energy.

Early 20th Century Proves Progress

The early 1900s saw many exciting discoveries about radioactivity. While working with thorium, Rutherford had detected radioactivity throughout his laboratory—even after the thorium had been removed. He deduced that this radioactivity came not from the thorium itself, but from a gaseous product of thorium’s atomic disintegration. This realization led to the discovery of another radioactive element—radon.

Rutherford then postulated that radioactive elements spontaneously and continuously disintegrate to release radiation and produce a decay chain of other radioactive elements and isotopes. He also learned that radon’s intense radioactivity decreased by half every few days. His term “half-life” is now used to describe the speed at which unstable atoms undergo atomic disintegration.

Rutherford observed that an inverse relationship existed between half-life and the intensity of radioactivity. Uranium, with its low level of radioactivity, has a very long half-life of more than four billion years. But extremely radioactive elements such as radium and radon have very short half-lives. Unfortunately, the effects of ionizing radiation on living tissue were not understood. While exposure to radioactivity seemed to halt the growth of certain cancers, it also caused burns and open lesions on the skin of many researchers. Nevertheless, hopes that radiation would cure cancer and boost general well-being created a huge demand for radium, some for research purposes, but mostly to be used in patent medicines and bizarre therapeutic devices.

Mining Uranium Ore

The aspect of research triggered the first significant mining of uranium ore—not for uranium, but the ore’s tiny traces of radium. The important radium sources were uraninite from the historic Joachimsthal mines in what is now the Czech Republic and the carnotite (hydrous potassium uranium vanadate) ores of western Colorado. By 1912, radium was the most valuable commodity in existence and cost $100,000 per gram—nearly $2.5 million in today’s currency.

Initially, radioactivity could only be detected with photographic plates and fluorescent screens; it could be crudely measured with gold-leaf electroscopes and complex, piezoelectric-quartz devices. Then in 1908, German physicist Hans Geiger (1882-1945) constructed a sealed, thin metal cylinder with a wire extending down its center. After filling the tube with inert gas, he applied an electrical voltage almost strong enough to pass between the electrodes, in this case, the wire and the tube walls. When exposed to radioactivity, the gas ionized to become conductive, completing the circuit and producing an audible click. These electrical discharges instantly returned the gas ions to their normal energy level, making it possible to continuously and immediately detect additional radioactivity and measure its intensity by “counting.”

Although the first “Geiger counters” were ponderous instruments sensitive only to alpha particles, they were vital to the early studies of radioactivity. In 1928, Geiger and his colleague Walther Müller designed a new tube. Now known as the Geiger-Müller counter, it is sensitive to all forms of radioactivity and is still used today.

Greater Understanding and More Utilization

The uses, perception, and importance of radioactive minerals changed radically during World War II when uranium became the source of its fissionable U-235 isotope needed for the first atomic bombs. Following the war, the United States government subsidized the “Great Uranium Rush,” in which improved, lightweight, shoe-box-sized Geiger-Müller counters were the key tools for the thousands of radiometric prospectors who searched for “hot rocks,” mainly uraninite and carnotite. The radioactivity emitted by uranium and thorium has several effects on minerals, one of which is color alteration.

Long-term exposure to low-level radioactivity can disrupt normal electron positions in the crystal lattices of certain minerals. This activity creates electron traps, called “color centers,” that alter the mineral’s color-absorption-reflection properties. The colors of smoky quartz, blue and purple fluorite and halite, brown topaz, and yellow and brown calcite are often caused by exposure to geophysical radiation.

Metamictization

Another interesting effect is metamictization, which occurs in some minerals that contain accessory amounts of uranium or thorium. In metamictization, geophysical radiation displaces electrons to slowly degrade the host mineral’s crystal structure. Metamictization is usually apparent in crystals as rounded, indistinct edges, curving faces, and decreased hardness and density. Metamictization can sometimes completely degrade crystals into amorphous masses.

Metamictization is common in the rare-earth minerals gadolinite (rare-earth iron beryllium oxysilicate) and monazite (rare-earth phosphate). Because of their similar atomic radii, uranium and thorium often substitute for rare-earth elements to make their minerals radioactive. California’s huge Mountain Pass rare-earth-mineral deposit was actually discovered by a uranium prospector equipped with a Geiger-Müller counter.

Zirconium Silicate

Zircon, or zirconium silicate, another mineral subject to metamictization, has an additional connection to radioactivity and is employed in radiometric dating, which uses known rates of atomic decay to determine the age of ancient rocks. Because of similar atomic radii, uranium substitutes readily for zirconium in zircon. The uranium-238 isotope has an extremely long half-life of 4,468 billion years. The inert, extremely durable zircon “protects” the traces of uranium—an ideal combination for the radiometric dating of ancient rocks.

When igneous rocks solidify from magma, their contained traces of uranium have not yet begun to decay. By measuring the extent of atomic decay, geophysicists can determine when the sample crystallized. The oldest known rocks are found in Australia. Based on partially decayed traces of uranium-238 contained in tiny zircon crystals, these rocks have been dated at 4,374 billion years—only a few hundred million years after the formation of the Earth itself.

Detecting Radioactivity

Today, mineral collectors have access to a wide range of radioactivity-sensing instruments, including dosimeters that measure cumulative radiation exposure, miniaturized Geiger-Müller counters, and scintillators that quantitatively measure geophysical radioactivity, and radiation monitors that measure relative overall radioactivity. Prices for basic instruments begin at about $40, while top-of-the-line, quantitative instruments can cost thousands of dollars.

Choosing the Radiation Monitor For You

For general mineral-collecting and amateur radiometric-prospecting uses, radiation monitors, which cost from $200 to $700, will suffice. I’m familiar with the Radalert™ radiation monitor manufactured by International Medcom of Sebastopol, California. It weighs 10 ounces and contains a miniaturized Geiger-Müller tube. Alpha and beta particles, gamma rays, and X-rays ionize the tube’s gas atoms, causing the tube to discharge with tiny electrical pulses. Integrated circuits convert these pulses to liquid-crystal displays, flash light-emitting diodes, and generate audible clicks.

This instrument detects total ionizing radiation (a mix of geophysical,

cosmic, and man-made radiation) and provides relative, rather than absolute or quantitative, radioactivity measurements. It is ready for use after quickly determining the local background radiation “load,” which varies with geology, solar-flare activity, and elevation.

At sea level, the normal background radiation might be roughly 13 counts per minute. But at a mountain elevation of 7,000 feet where there is less atmospheric shielding of cosmic radiation, the background level might be 30 counts per minute. Radiation monitors can even detect temporarily elevated levels of cosmic radiation due to increased sunspot activity.

Background Radiation

Background radiation also varies with local geology. Radiation levels near granite outcrops are usually higher than in other areas because of traces of uranium within the granite. Radiation monitors can serve as a safety tool to detect elevated levels of radioactivity from potentially hazardous accumulations of radon gas in living spaces. They can also detect the very low levels of alpha radiation emitted by household smoke detectors.

Smoky quartz sometimes has detectable traces of radioactivity, while gadolinite, monazite, and other rare-earth minerals have levels that are easily detectable. When used with such uranium-bearing minerals as canary-yellow carnotite and tyuyamunite, yellowish-green-to-green autunite, and green torbernite, radiation monitors “sound off” with hundreds or thousands of counts per minute.

Among the interesting radioactive collectibles is yellow “uranium glass,” which was popular in the early 1900s and still emits detectable levels of radioactivity. Another is greenish trinitite, quartz sand that was fused together by the world’s first atomic detonation on July 16, 1945, at New Mexico’s Trinity Site. Trinitite specimens, which are still sold today, have low but easily detectable levels of radioactivity.

Proper Handling

Collecting radioactive minerals is not dangerous when precautions are followed. One rule is to collect small specimens. Cumulative radiation and the amount of radon gas emitted by radioactive specimens are directly proportional to specimen size. There is no need to collect cabinet-sized specimens of carnotite, even though they are easily found on mine dumps.

Handle radioactive specimens minimally and always wash hands thoroughly afterward. Never eat, drink, sleep or, smoke around radioactive specimens, and always keep them out of the reach of children. Also, radioactive specimens should be clearly labeled as such and stored in well-ventilated spaces away from living areas.

Radiation monitors can add a new dimension to many field-collecting trips. And they are an absolute necessity when exploring the thousands of uranium mine dumps scattered across the Four Corners regions of Colorado, Utah, and New Mexico. Radiation monitors make the difference between finding nice specimens of brightly colored, oxidized uranium minerals and finding nothing at all.

Collectors should never enter an abandoned mine, but abandoned uranium mines are particularly hazardous. These unventilated mines have accumulated extremely high concentrations of intensely radioactive radon gas.

Anyone interested in the history of radioactivity will enjoy visiting these two New Mexico museums: The Bradbury Science Museum at Los Alamos National Laboratory in Los Alamos, and the National Nuclear Museum of Science and History in Albuquerque. Both contain a wealth of exhibits and information on radioactivity—one of the fascinating physical properties of minerals.

This story about radioactive rocks previously appeared in Rock & Gem magazine. Click here to subscribe. Story & photos by Steve Voynick unless otherwise indicated. 

The post Radioactive Rocks: A Rockhound’s Guide first appeared on Rock & Gem Magazine.

Minerals are all around us and even within us. Consider iron in your blood or calcium in your bones. While humans have always sought food products, we’ve always used rocks. Our ancestors used cobbles as hammers to crack nuts. We later learned to use obsidian, chert, and flint to knap knives and spear points and to spark fire. We’ve moved on from the Stone Age to the Copper, Bronze, and Iron Ages. Minerals and related earth resources continue to enable contemporary life and the built environment in which we live. They include metals, nonmetallic minerals, and fossil fuels. How little we appreciate this fact of life!

Take the Common Pencil…

Something as simple as a pencil requires more minerals than you might imagine. While a pencil casing is painted wood with a hollow core, the rod within the core is a combination of graphite (carbon) and kaolinite (clay). The more kaolinite, the harder the rod. This is why we have #2, #3, and other pencil grades that leave either a wide dark streak or a slender light streak. While the pencil eraser is a natural or synthetic rubber, it may contain pumice to provide grit. Holding that eraser to the pencil is a tube constructed of aluminum (from bauxite) or brass (from copper plus zinc, or sphalerite). Four to six minerals in a common pencil. Who knew?!

To appreciate the number of minerals used in everyday life, deconstruct other objects. A salt shaker often has an aluminum top (derived from bauxite) and a glass body (from sand, or silicon dioxide) and is filled with salt (halite) crystals. Although it’s on its way out, an old-fashioned incandescent light bulb has a glass exterior (made from silica, soda ash, lime, coal, and salt), a brass or aluminum screw-in base, a tungsten filament, copper and nickel lead-in wires, molybdenum tie and support wires, and an aluminum heat deflector.

Explore Minerals Contributing to the Build Environment

Here are some fun and easy exercises to introduce kids (and yourself ) to the many minerals contributing to our built environment.

Match the Product to the Mineral

An Interactive Display & Quiz

Perfect for a school project…Construct an interactive display showing everyday items at the back and the minerals that went into them at the front. For instance, a soda can at the back and a specimen of bauxite (aluminum ore) at the front, or matches at the back and sulfur at the front. Provide a quiz for kids to fill out to match a mineral to a product.

Spin the Wheel!

For more immediate interactive fun, have a board laid out with squares numbered and stocked with different economic minerals. Kids spin the wheel. They then need to name a product made from a mineral on the number where the wheel lands. If they guess correctly, they keep the mineral. Stick with fairly easy and obvious choices (e.g., a copper nugget matched to plumbing pipes) and have a poster or chart nearby that kids can consult.

The Home Scavenger Hunt

In a school classroom, rock club meeting room, or a home, gather kids around a flipchart, chalkboard, or whiteboard. Encourage them to look around and list everyday things and the rocks and minerals that went into them. If using an old-fashioned chalkboard, you can start with the chalk and the slate of the chalkboard. You might go throughout an entire house, or focus on a particular room.

Here are just a few examples: a brass lamp, windows made of silica, many things made of plastic derived from petrochemicals, fireplace bricks derived from clay (kaolinite), a tin cup, a gold wedding ring, walls made of plasterboard comprised of gypsum, steel nails, and screws in the furniture and paint on the walls containing diatomite as filler.

A Hardware Store Scavenger Hunt

Take a field trip for a scavenger hunt at a hardware store. To get started, here are a few things to seek:

• aluminum and tin siding or roofing (from bauxite or cassiterite)

• bricks and ceramic products (from fired clay, or kaolinite)

• diatomaceous earth for swimming pool filters

• drill bits and saw blades used for cutting tile, concrete, etc. (from diamond)

• electrical wiring, pipes, and plumbing fixtures (from copper)

• glass (from silica sand)

• plaster and drywall (from gypsum)

• rough and crushed rocks and stones for ornamental use (scoria, limestone, marble, etc.)

• sand for mixing with concrete, for sandboxes, etc.

• slabs of various sorts (granite, marble, etc.) for kitchen countertops

• steel and iron nails (made from iron ores like hematite)

Make Your Own Collection

Entire collections can be made of the raw materials of our built environment. Many common minerals are inexpensive and readily available from show dealers. As a start, consider pennies and a copper nugget; nails and hematite; fluorinated toothpaste and a fluorite crystal; laundry detergent and borate minerals; table salt and halite crystals; matches and sulfur.

Learn More!

Several websites provide handy tables linking minerals to everyday objects. Here’s a sampling:

• Minerals Education Coalition

• Women in Mining

• United States Geological Survey (USGS)

• American Geosciences Institute (AGI)

• Gemological Institute of America (GIA)

• National Mining Association

• AFMS Future Rockhounds of America Badge Manual

How Minerals Shape History

As we humans progressed from the Stone Age to the Electronic Age, we’ve seen all sorts of ages in between dominated by a search for earth resources. Consider gold rushes, wars of conquest for mineral-rich colonies, and “titans of industry” (Carnegie, Rockefeller, Peabody, Getty). Our current age is obsessed in a quest for minerals for electric batteries built with lithium, and cobalt. These resources are eagerly being sought to move us from a carbon-emitting petroleum-dependent economy to one based on clean energy.

However, keep in mind that clean electric energy still requires dirty mining. If you think we can get to a so-called no-cost energy future, think again! There will always be a need for mining and minerals, along with a cost to pay. How we ultimately balance such costs is what matters. Think we can live without minerals and all that goes into extracting them? Think again. Think wisely.

What Made It?

Pencils or smartphones are just the beginning. There are thousands of minerals and even more applications of those minerals. Here’s a tiny selected sampling…

This story about the minerals used in everyday life previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Jim Brace-Thompson.

The post Minerals Used in Everyday Life first appeared on Rock & Gem Magazine.

Memento Mori

A skull is a common motif for the Latin phrase, “Remember you will die” and the ancient practice of reflecting on one’s mortality, going back to the time of Socrates, who is said to have believed the only proper practice of philosophy was “about nothing else but dying and being dead.”

Well, that’s no fun. Even at Halloween. Thank goodness for Canadian actor, comedian, filmmaker, musician and producer, Dan Aykroyd, and world-renowned American portrait and landscape artist, John Alexander. They mastered mixing good taste, good spirits and Herkimer diamonds into a trio of ultra-premium vodkas, in bottles sure to encourage philosophical musings, called Crystal Head.

Clearly Inspired

“The bottle was designed by creative people with the creative spirit in mind, “ says Dana Miller of the New York City-based KLG Public Relations representing Crystal Head Vodka. “Dan and John designed the skull-shaped bottle as a symbol of life, reflecting power and enlightenment. Creativity is at the heart of Crystal Head, with a desire to inspire those who think differently and encourage their creative pursuits.”

Each bottle is the result of using the highest quality ingredients and water from Canada’s eastern province of Newfoundland to produce three additive-free vodka expressions: Original (locally sourced Canadian corn), Aurora (English wheat) and Onyx (Blue Weber Agave sourced from a single farm in Mexico). The origin story starts around 2007 when Aykroyd was bedeviled by an inability to find additive-free vodka spirits to enjoy. So the three-time Ghostbuster decided to make his own.

Filtering the Vodka

After the vodka is distilled four times into a neutral grain spirit and blended with pristine provincial water, the seven-time filtration process includes a final series of three filtrations through layers of the semi-precious crystals found almost exclusively in central New York State: Herkimer diamonds.

The result is a spirit as clear and colorless as the natural gems, with a silky smooth taste and a wraithlike wafting of neutral grain aromas with hints of citrus.

“Aykroyd’s process of distilling quadruple times, and filtering seven times, with the final three through Herkimer crystals, makes this vodka easy drinking. It’s slightly sweet and smooth, and offers a hint of vanilla,” reviewed Jill Weinlein in 2020 for JustLuxe.com.

Three final filtrations through Herks also craft Crystal Head’s Aurora, which uses a different grain to produce drier, bolder vodka with hints of anise and peppercorn, and the bottle’s iridescent metalized finish is described as a “tribute to this natural wonder of the world.”

This stark reminder of mortality has evolved into an artful tribute. Crystal Head Vodka celebrated its 10th anniversary with a John Alexander Artist Series Halloween Limited Edition bottle (since sold out at about $700 for a No.1 bottle).

Legends in the Making

Aykroyd’s collaboration with Alexander (whose works are in the Metropolitan Museum of Art, Corcoran, and Smithsonian Museums) began with a shared interest in a Mesoamerican legend about 13 crystal skulls before filtering down to natural crystals almost as legendary in their own right.

What is true is that ancient solid crystal skulls exist. Yes, just like Indiana Jones and the Kingdom of the Crystal Skull. Legend has it that 13 (or 52, as in four sets of 13) of these powerful transmitters of energy are destined to reunite in a circle — a dozen heads, plus one in the center – at a psychically profound cosmic juncture in the human experience.

How Many Skulls?

Surrounding that supernatural speculation, National Geographic science writers Richard A. Lovett and Scot Hoffman add, “There are perhaps a dozen of these rare crystal skulls in private and public collections. Some are crystal clear, others of smoky or rose-colored quartz. Some are actual human size and of very fine detail, while others are smaller and less refined.”

“Thirteen of these polished skulls have been found on our planet,” Aykroyd said in a 2011 interview. “Eight are in the possession of individuals and institutions. Five are missing. Of the eight, each one is unique. Some are green, orange, cloudy and crystal clear.

They are believed to be thousands of years old and appear to have been carved over several hundred years but don’t bear any tool marks. Their very construction defies common logic.”

Attracting Positive Energy

What is clear is that a belief in such crystal figurines to attract positive energy and enlightenment inspired both actor and artist to create Crystal Head as the ultimate vessel for an additive-free, “pure spirit” vodka.

Bruni Glass of Milan, Italy, manufacturers of the bottle, seem to agree. Meanwhile, 300 million years earlier, crystals destined to become ‘spirit stones’ for early North American nations were busy forming.

About Herkimer Diamonds

One of seven rare gems and minerals found in New York State, Herkimer County diamonds, or simply, Herks, belong to the same geologic region of the Mohawk Valley made famous in The Last of the Mohicans. Here ancient dolostone and limestone rock, porous enough to allow mineral – and silicon-bearing fluids to flow through, seeped into a massive network of tectonic fissures and fault lines.

Unlike most quartz found in igneous rock, nascent Herks exhibit an antipathy to attachment, thriving instead in free-floating pockets of liquid inside fault line cavities, or vugs. The results of such disconnection to a host rock are doubly terminated hexagonal quartz crystals, including barbells and scepters.

Herk Facts

Prized for their innate beauty, Herks range from water-clear to smoky black and are purported to have abilities, as holistic tools, to receive and transmit energy. Many people head to this region today to hunt for Herkimer diamonds.

Early Mohawk peoples referred to themselves as Kanyenkehaka, or ‘People of the Crystals,’ says Larry Michon, president of Northern Berkshire Mineral Club (NBMC), and the valley where they lived was called Kayenkehaka or ‘The Place of Crystals.’

The “diamonds” (a 7 on the Mohs scale) were so prevalent that early settlers found them in stream sediments and plowed fields and, according to Schiffer Publishing’s Collectors’ Guide to Herkimer Diamonds (2014), “immediately held them in high esteem.”

Until the 1600s, when European-crafted glass beads usurped the sparkling crystals in New World popularity, they were traded among neighboring villages, used to make tools, and crafted into amulets. Now, Herkimer diamonds can add ‘vodka filtration’ to their resumé.

Cold Comfort 1 ½ oz. Crystal Head Vodka 1 oz. Dark Rum 4 oz. Apple Cider 1 Cinnamon Stick Add Crystal Head Vodka, dark rum and apple cider in a cocktail shaker with ice. Shake vigorously for 10-15 seconds. Strain into a glass with ice. Garnish with cinnamon stick, finely grated cinnamon and thinly sliced apple.

Through the Glass, Darkly

An appreciation for the power of gemstones to potentially imbue metaphysical properties led Crystal Head Vodka to work with a second stone: onyx.

According to the International Gem Society (IGS), this variety of chalcedony has a mystical association with capturing and containing demons or imps.4Scott Cunningham’s Encyclopedia of Crystal, Gem & Metal Magic also refers to onyx as useful for temporarily containing energy of any kind and the blackness of the stone allows easier access to the subconscious mind.

Sounds like a perfect container for a spooky season’s spirits. Crystal Head describes Onyx, one of the first commercially available agave-based vodkas, and its luxurious glossy black bottle with matching crest debossed cap as, “a celebration of the powerful, warrior crystal.”

“The story behind Crystal Head is one of positive spiritual energy,” Aykroyd has said and, thanks now to Herkimer diamonds, skulls are more than memento mori. They carry good gemstone energy and, like the ancient crystal legend, become “symbols of enlightenment and hope for a better future.” We’ll drink to that.

This story about Herkimer diamonds and Crystal Head vodka appeared in Rock & Gem magazine. Click here to subscribe. Story by L.A. Sokolowski.

The post Herkimer Diamonds & Crystal Head Vodka first appeared on Rock & Gem Magazine.

Everything is Energy

While this connection might seem puzzling on the surface, it all boils down to energy. Samantha Fey, author, teacher and co-host of the podcast, Psychic Teachers, said, “Crystals have the piezoelectric effect, so they do generate energy. They grow with their own unique vibration and lattice structures.”

This phenomenon occurs when pressure is put on particular crystals, such as quartz, causing the atoms within the stone to move, subsequently turning mechanical energy into electrical energy. This is why crystals are used in watches, televisions and cell phones. It’s this inherent energy that resonates with astrological signs.

Connecting Zodiac Crystals & Sun Signs

Those who are familiar with astrology understand the correlation with the elements — fire, water, air, and earth — and how they offer a glimpse into personality characteristics. When working with crystals according to sun signs, it’s helpful to consider the elements and how they best fit with the particular stones.

Fey used an example of the sun sign Cancer, which is attributed to the moon and is a classic water sign. “They are very watery and ruled by their emotions. Look for crystals with those similar qualities,” she said, such as moonstone.

It’s also important to understand how a stone works with a particular sign in coordination with where we are physically, mentally, and spiritually. “Our energy fluctuates up and down all the time,” Fey said. Depending on what we need, crystals can amplify or balance our actions.

While there are classic combinations of crystals and Zodiac signs, such as obsidian with those under Scorpio, in reality, there are multiple crystals per sign. The choice depends on what you need to do or learn, and this list is a good start to finding a crystal that works for you.

Aries Sign

Notoriously stubborn, Aries people know what they want and are clear about who they are. Fittingly, amazonite is an ideal crystal for this sun sign as it enhances inner strength and the warrior attitude, particularly with women going through significant changes in their lives.

“It’s called the stone of hope and new beginnings,” said Fey, and is excellent for manifesting dreams and goals.

Deb Bowen, co-host on Psychic Teachers, as well as a metaphysical teacher and author, recommends Sardonyx because it is excellent in the realm of self-control and discipline.

“It’s really good for communicating relationships,” she noted because Aries can have sticking points in this area.

Taurus Sign

An earth sign, Taureans, are grounded people who are nurturing and comforting to those most important to them. Being a bull, they are known for their stubbornness and uncompromising nature.

The beautiful light blue to green, or sometimes white kyanite is good for Taureans because it helps clear and align the chakras, according to Bowen. It also builds stability and trust and is excellent for communication. Kyanite cannot hold negative energy.

Fey recommended, ”Carnelian is a great stone for bringing in creativity, positivity and joy. It’s the cheerleader of the stones and it keeps the other stones together.”

Gemini Sign

When a “twin” is around, there’s never a dull moment. Geminis are known to have lots of energy and are very talkative. They can also be indecisive and impulsive.

The green and smooth gem serpentine is a good fit for a Gemini. “It helps you to align your soul’s purpose,” explained Bowen as it enhances the heart chakra. She noted that it also offers protection against the dark arts.

Cancer Sign

Cancer is the classic mother of the Zodiac who is family-oriented, intuitive, and a tad moody. Not surprisingly, the “crab” is their sign.

Bowen said, “Sometimes cancer folks can get sad or depressed.” Because of this tendency, she said blue chalcedony is a good choice. “It helps cancer to communicate the truth. It also dispels negative energies and activates positive changes. It’s a great stone for those who seek general positive shifts in their lives.”

Leo Sign

Leo is known to love being the center of attention with their bigger-than-life energy. They’re also loyal, generous, and loving. The funny thing is, their negative traits simply seem to be their positive traits on overdrive.

Because of this desire to shine, citrine is the stone for Leos. ”Citrine is like your own personal sun,” said Fey. This yellow-to-orange type of quartz appears charged by the sun. Unfortunately, natural citrine is a rare stone and much of what we find is heat-treated amethyst (enhanced gemstones). It’s also well-known to manifest abundance, a natural quality of Leos, and is sometimes called the “stone of success” or the “merchant’s stone.”

Virgo Sign

Logical and energetic, Virgos thrive with well-organized and practical goals, while on the flip side, they tend to overthink situations and can often seem aloof and detached.

Resembling the blues and greens of the earth, the mineral chrysocolla is often found in copper deposits and referred to as the “Stone of the Goddess,” with famous figures, such as Cleopatra, valuing its beauty and energy.

Fey said chrysocolla is like a happy-go-lucky friend. “It’s a great stone for everything. It helps people face some hard truths,” she said. She also recommended that those working with this stone visualize their goals going into the stone.

Libra Sign

The scales represent Libra’s desire for fairness and balance, which is the center of this witty, smart and outgoing soul. With Venus as their ruling planet, they are all about love but will carry a grudge if slighted.

“Libras look at both sides differently, or rather it’s difficult to choose sides,” said Bowen, who is a Libra. She said bloodstone is good because it balances everything, including Libra’s energy. “It helps level folks be present in the here and now.”

Scorpio Sign

Scorpios get a bad rap as being secretive, defensive and vindictive, but their emotions run deep (even if they don’t show it), and they are passionate about whatever, and whoever, they love.

“Malachite is the drill sergeant,” said Fey. “It’s the only stone that breaks to warn you when something wicked this way comes. It’s great for protection.” This rich green stone is also an important part of facing Scorpio’s shadow side. Fey said, “It’s like a friend that is in your face.”

Known as the stone of transition, Bowen said, “Charoite connects the heart and crown chakras.” It allows someone to focus on self-love when setting healthy boundaries.

Sagittarius Sign

Ruled by Jupiter, Sagittarius people are gregarious and big dreamers but can be blunt and preachy.

Fey recommends labradorite that resembles the aurora borealis with its color-shifting nature where one moment it looks gray, the next is shimmering blues and greens. “It helps block the emotions and stuff around you that’s not yours. It’s more like a filter. It lets the good stuff come in and the bad stuff goes out,” she said.

Capricorn Sign

With Saturn as the taskmaster, Capricorns get things done. Although they are disciplined and responsible, this can shift into a level of condescension toward others.

Amethyst is the go-to for these hardworking signs. “It cleans, clears, and heals everything around it,” said Bowen. ”It’s a balancing, protective and loving stone. It’s a great stone to connect. It fights off temptation and works with decision-making. It’s good for sleeping and it protects them from nightmares.”

Once used by the Romans to fend off the evil eye, tiger’s eye is protective and balancing. Fey said, “It works with your energy to establish a foundation and recognize patterns of things that no longer serve you. She said to place tiger’s eye on the solar plexus during meditation for courage and confidence, as well as to shift toxic energy into positive ones.

Aquarius Sign

Quirky and unconventional, the highly social Aquarians champion humanitarian efforts and relish deep conversations. Yet, they are not known for being the most emotionally open individuals and might appear aloof.

“Aquarians are ahead of their time,” said Fey. “Dark, ruby red garnets help them recharge and revitalize their energy. Write down goals and dreams for the year and place garnets on top of the list.”

The ornamental chrysanthemum stone is typically all black except for a splash of white in the middle resembling a flower. Bowen recommended it for Aquarians because ”it brings to us child-like energy and being able to live in the moment.”

Pisces Sign

The astrological fish who swim in deep waters are philosophical, intuitive and creative, yet at times, spend too much time in their own heads.

To counteract this latter tendency, aquamarine, which is often called the “stone of courage” boosts confidence for the Pisces people. Bowen said, “It’s such a beautiful stone. It helps one to always be prepared.” Legend says aquamarine was spilled from a mermaid’s treasure chest and it was supposedly blessed by Neptune.

Fey recommended fluorite to clear negative energy. Called the student’s stone, she said, “It’s created for cleansing the aura. It eliminates negative patterns and helps you to see your path more clearly,” said Fey. She also mentioned it is effective in blocking electromagnetic fields and is often kept near the computer to minimize exposure.

Picking the right stone for you is a matter of listening to the universe. “It’s really important when you buy sun sign crystals that the stone speaks deep, deep into your soul,” said Bowen.

“It’s great to read and study, but at the end of the day, you have to go with the crystal that resonates with you,” noted Fey. “Walk into a store that sells stones and see what you’re drawn to. Find your buddy and stick with it for a while.”

*The metaphysical properties discussed in this article are not intended as a substitute for traditional medical treatment. If you have a health issue, please seek a licensed medical professional. The crystals and stones discussed are not intended to diagnose, treat or cure any conditions.

This story about zodiac crystals previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Amy Grisak.

The post Best Crystals for Your Zodiac Sign first appeared on Rock & Gem Magazine.

Quartz crystals grow when atoms of silica and oxygen lock together in a regular and repeating pattern as silicon dioxide. When quartz crystallizes, its shape connects to its nourishment, or the physical and chemical conditions surrounding it. “Perfect” or “ideal” quartz has hexagonal (six-sided) crystals with triangular faces forming pyramids on top and bottom. But perfection is the exception.

How Do Types of Quartz Crystals Misgrow?

In nature, growth conditions constantly change and crystals become distorted. One crystal face may grow faster than others. Crystals may split and develop multiple points and faces. A crystal may be twinned or intergrown with others. It may stop growing, dissolve a bit and then resume growth. In short, don’t bet on odds for a perfect crystal in nature! Inclusions in quartz are not uncommon.

1. Gwindel

Also called quendel, gedrehten or twisted quartz, gwindel (pronounced “gvin-dell”) is another collection of many stacked crystals. In the case of gwindels, each crystal seems to have formed at a somewhat curved or bent offset from the others. The result is a slightly curved comb or toothed pattern.

2. Skeletal Quartz

Skeletal quartz (also called window or Fenster quartz) crystallizes in unstable conditions with more saturation than normal. This causes the edges to grow faster than the crystal faces so the edges stick out and the faces are set back like glass in a window frame giving it a layered or ribbed look. (Hence the name skeletal quartz.) There also may be etchings and cavities with clay minerals, gases or water trapped inside.

3. Phantoms

Quartz crystals developing within mineral solutions sometimes stop growing and then grow again later. In between, other minerals may get deposited on a crystal face. These leave spooky zones of different colors within the quartz, including blood red which comes from the iron mineral hematite. Crystals-within-a-crystal are referred to as inclusions or “phantoms.”

4. Faden Quartz

Faden means “thread” and in the case of Faden quartz, the name comes from the ghostly white line running through it. Faden quartz consists of a series of interconnected flat crystals. The white line is made from cracking during quick crystal growth and fluid trapped in the crack.

5. Twins

Twinning is common and comes in many varieties with quartz, including Dauphine law, Brazil law and Japan law. Japan law twins are a collector favorite. They were named after specimens from a classic locality in Kai, Japan.

6. “The Chiseler”

Rather than an even pyramid shape, chisel quartz has flattened crystals with a wide beveled (slanted and angled) face that looks like a chisel.

7. Spirit Quartz

Spirit quartz, also known as cactus quartz, consists of a primary crystal with prism faces covered by a druse of small second-generation crystals, much like the trunk of a cactus is covered by spines. It is said to be able to connect you with the “spirit realm.”

Collect Different Types of Quartz

Don’t fear skeletons and phantoms. Collect them! The weirder, the better! Each tells a story of growth and misgrowth within the quartz crystal family.

This story about spooky types of quartz crystals appeared in Rock & Gem magazine. Click here to subscribe. Story and photos by Jim Brace-Thompson.

The post 7 Spooky Types of Quartz first appeared on Rock & Gem Magazine.

January

Garnet has been the birthstone for January since the 15th century, at least. With a Mohs hardness of 6.5 to 7.5, it can be faceted into beautiful gemstones that wear well in jewelry. Since the term “garnet” actually refers to a group of nesosilicate gems, those born in this month can choose from a rainbow of colors.

The most common members are red almandine, an iron-aluminum silicate; red pyrope, a magnesium aluminum silicate; orange-yellow spessartine, a manganese aluminum silicate; the yellow or green varieties of andradite, a calcium-iron silicate; predominately green grossular, a calcium-aluminum silicate; and rare, bright-green uvarovite, a calcium chromium silicate.

February

From the 15th century to the present, amethyst has been the preferred birthstone for February. Amethyst belongs to a mineral family that can compete with garnet for diversity of color: quartz.

Pure quartz is colorless, as exemplified by Herkimer diamonds. The causes of amethyst’s shades of pale violet to rich purple are radiation and the inclusion of iron impurities and trace elements.

As a rule, amethyst crystals are short and stubby, and occur in large numbers, often filling a large vug a hollow petrified tree section, or lining the inside of a geode. Fine crystals that are large enough to produce a faceted gem of over 20 carats are rare.

March

The current choice of a birthstone for March is aquamarine. Aquamarine is a variety of beryl (Mohs 7.5-8). Its name was derived from the fact that the beautiful, transparent, blue-green coloration of the gem resembles that of seawater. It can be found in translucent to transparent crystals that form in the hexagonal system. The six-sided crystals are often striated lengthwise.

Aquamarine develops in metamorphic rocks and, more often, in pegmatites.

April

Before 1900, a person with an April birthday had two choices of birthstone: diamond or sapphire. During the 20th century, however, diamonds became the preferred stone.

Diamond, a mineral consisting of pure carbon, heads the list of all gemstones for its beauty and hardness. A 10 on the Mohs Scale of Hardness, it is resistant to scratching and is an ideal gem to set in rings. Its hardness results from the arrangement of its atoms in cubes.

All diamonds have slightly rounded faces, and they’re so smooth they feel greasy to the touch. They can be colorless and water clear to blue, pink, yellow, brown, green or black, and transparent or translucent. They shine with an adamantine luster when held to the light.

May

There were two choices for May birthstones for several hundred years: emerald and agate. The popularity of agate seems to have waned at the turn of the 20th century, so emerald is now the favorite. It’s the green member of the beryl family of gemstones. The color varies from bright green to pale green and, sometimes, darker shades of blue-green.

Fine emeralds have a velvety surface appearance and, in the better stones, an even distribution of color. One bad trait of emeralds is a tendency to have inclusions. It’s rare to find an emerald without some slight imperfection. This in no way deters from the beauty of this gemstone, though. It can also be one way of determining whether an emerald is a simulated gem or the real thing, as manmade stones have no imperfections.

June

The contemporary choices for June are pearl, moonstone and alexandrite. Of course, a pearl is the organic product of marine bivalves and not a mineral.

Moonstone is a variety of feldspar that shows adularescence, or schiller, an optical effect that produces a milky luster with a bluish tinge that appears to move across the stone when it is tilted. The phenomenon is named after the feldspar variety adularia.

Alexandrite is a color-change variety of chrysoberyl (beryllium aluminum oxide). This is a very rare and expensive gemstone. It has a hardness of 8.5, and its crystals are either tabular or prismatic. The distinction between alexandrite and chrysoberyl is simply color. A strange characteristic of alexandrite is that it is red, purple or violet when held under artificial light, but in daylight, it looks green.

July

Ruby is the standard birthstone for the month of July. It is a corundum (aluminum oxide) gem that gets its color from the presence of chromium in its structure. An exceptionally hard mineral, corundum illustrates a hardness of nine on the Mohs scale. “Pigeon-blood” red is the preferred color for rubies, though they also occur in lighter shades, including pink. All other colors of corundum are called sapphires.

Ruby exhibits all the desirable properties of a jewelry stone: beauty, durability, optical properties, and rarity. Some rubies display a star or asterism when fashioned into a cabochon. This effect is caused by the reflection of light from numerous inclusions of minute, needle-like crystals of rutile. Corundum crystallizes in the hexagonal system with a tabular-barrel-shaped habit.

August

Current birthstones for August are peridot, the gem-quality form of olivine and spinel. Olivine makes up a large portion of the earth’s mantle. Rocks containing olivine have been brought to the surface by volcanic action and actually blown out in the form of volcanic bombs. Masses of olivine have been found in meteorites, and the Apollo astronauts brought basaltic rocks back from the moon that contained olivine.

A popular jewelry stone, peridot has a hardness of 6.5-7 and can be transparent or translucent, with a vitreous luster. Its color shades from deep green to apple green, yellow-green or olive. It’s most often found in granular nodules, forming short, prismatic crystals in the orthorhombic system.

Spinel is the gem-quality member of the larger spinel group. Its hardness (Mohs 7.5-8.0) makes it ideal for jewelry use. Its spectrum of colors includes red, pink, purple, blue and lavender. In times past, red spinel was often mistaken for ruby. A notable example is the Black Prince’s Ruby, set in the royal crown of England.

September

The birthstone for September is sapphire. This term refers to any corundum (aluminum oxide) gem that has any color other than red (ruby). Sapphires may be colorless, blue, green, yellow, orange, brown, pink, purple, gray, black, or multicolor. At Mohs 9, its hardness is second only to that of a diamond.

Heat treatment is sometimes used to give natural blue sapphires a deeper, more pleasing color. Natural star sapphires, which display the optical phenomenon of asterism, are very rare.

October

Two options for October are opal and tourmaline. Opal is a magnificent gemstone with a play of color or “fire” in all colors of the spectrum. Spaces between the tiny spherules of silica that make up the gem diffract light into its spectral colors. Red, yellow, green and blue, in strong to pastel shades, flash from the stone when it is tilted.

Opal occurs in common and precious types. Common opal does not display any reflective fire. It may have a honey-yellow, brown, gray or colorless body color that is milky and opaque. Opal (Mohs 5-6) is not a very hard gemstone.

Tourmaline, a silicate of boron, has a complicated chemical composition, in which a number of elements, including calcium, iron, sodium and aluminum, may combine. It has a Mohs hardness of 7-7.5.

It belongs to the trigonal crystal system and its habit is hemimorphic (a crystal having two ends of an axes unlike in its planes).

Because of the coloration of the individual stones, tourmaline has several names, including schorl (black), rubellite (red), indicolite (blue), and dravite (brown). Tricolor crystals are common. The popular watermelon variety has an outer layer of green around a red core.

November

The current birthstones for November are topaz and citrine. People tend to think of topaz, a silicate mineral with aluminum and fluorine, as a yellow stone, but heat-treating and color-enhancing adaptations have made blue the predominant color on the market. It is an allochromatic mineral, which means its color is caused by internal defects in the crystal and has a Mohs hardness of eight.

Citrine is the golden member of the quartz family (silicon dioxide). Though quartz in its many forms is one of the most abundant minerals on earth, fine, gem-grade crystals are not that common. Citrine is affordable and, when faceted, rivals more expensive gemstones in beauty.

December

There are three birthstones for December: turquoise, blue zircon and tanzanite. Turquoise (hydrated copper aluminum phosphate) is an opaque, blue-to-green, massive gem material. It has a relatively low hardness of Mohs 5-6, so care must be taken with turquoise jewelry.

The rarest and most valuable variety is robin’s-egg blue with black “spiderweb” veins of limonite. Fake turquoise, consisting of dyed howlite or magnesite, is common. Buyer beware.

Zircon (zirconium silicate) can be blue, black, red, brown, green, yellow, smoky, or water-clear. It has an adamantine luster much like that of a diamond, and it is often misidentified as such.

Tanzanite, the blue/purple variety of zoisite (basic calcium aluminum silicate), is a recently introduced alternative for December. Tanzanite crystals in shades of yellow to brown, green, pink, gray or blue are often heat-treated to produce a gemstone that is a beautiful and permanent blue.

This story about what are birthstones by month previously appeared in Rock & Gem magazine. Click here to subscribe! Story by Kenneth H. Rohn.

The post What are the Birthstones by Month? first appeared on Rock & Gem Magazine.

Tourmaline Colors

One reason for tourmaline’s popularity is its wide array of colors – over 100! The mineral colors are caused by traces of different chemicals. For example, iron produces blue (indicolite) and green colors and manganese produces pink and red colors. Sometimes tourmaline colors are enhanced by heat treatment.

There are five major tourmaline species.

1. Dravite

2. Elbaite – Named after Elba, Italy. Most gem varieties occur in this species.

• Rubellite – Pink
• Paraíba (named after Paraíba, Brazil)
• Watermelon Tourmaline – (red center and green rind)

3. Liddicoatite

4. Schorl – Black (colored by iron)

5. Uvite

Tourmaline may form beautiful, elongated crystal clusters that are highly sought after by collectors. It is one of the most prized minerals and stunning specimens can be among the most aesthetic examples in the mineral kingdom.

Tourmaline Facts

Tourmaline has a Mohs hardness of 7.5 and crystallizes in the trigonal system. Most crystals are striated, elongated and prismatic. Vitreous luster and conchoidal fracture are also characteristic. Chatoyancy (cat’s eye effect) is found in some tourmalines.

Besides its use in jewelry, tourmaline becomes electrically charged when it’s heated. Piezoelectric properties can make tourmaline useful in the manufacture of various industrial gauges.

Confident Tourmaline

In the metaphysical realm, tourmaline is thought to give confidence, relieve nervousness, promote self-assurance, increase physical energy, enhance the immune system, help negate negative thoughts and relieve tension.

Tourmaline is the gemstone for the eighth anniversary and a birthstone for October.

Where to Find

Afghanistan; Australia; Brazil; China; Congo; India; Italy; Kenya; Madagascar; Mexico; Morocco; Mozambique; Myanmar; Namibia; Nepal; Nigeria; Pakistan; Russia; South Africa; Sri Lanka; Sweden; Tanzania; Thailand; United States of America; Urals; Zambia

This story about tourmaline previously appeared in Rock & Gem magazine. Click here to subscribe! Story by Richard Gross and Pam Freeman.

The post Tourmaline: Properties and ID first appeared on Rock & Gem Magazine.