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.

Arsenic is a lethal poison, but nature uses it to create some very beautiful minerals. We are all familiar with the more important arsenides, like primary arsenopyrite, and secondary arsenates like adamite and legrandite are very well known and frequently discussed. These are the subjects of a later article.

That leaves a large suite of arsenic species that may be less widely known, but certainly eagerly sought by collectors. Others are so uncommon or rare that they do not lend themselves to the collector market.

Uncommon And In Demand

Quite uncommon species that are still well worth describing because they are in demand among collectors are arsenic species like liroconite, clinoclase, olivenite and chalcophyllite, which are very attractive and have been found in well-crystallized specimens.

The mines of Cornwall, England, which produced arsenopyrite as one of their major ores, are well-known sources of these four secondary species. Arsenic, a semimetal, and the metals copper and tin were abundant enough to be mined and processed there.

The element arsenic has been recognized for centuries. It was among a small group of native elements long known to the ancients who dabbled in alchemy, the pseudo-science of the Dark Ages. Researchers doubt pure, or native, arsenic was well known in those ancient times, as it has always been a very rare natural element.

What the alchemists called arsenic was more likely common arsenic sulfides, like orpiment and a mineral they called “sandarac”, most likely a form of realgar. It was not until the silver mines in Germany opened around 1000 CE that actual native arsenic was found in several silver mines at Freiberg (Saxony), Joachinsthal (Bohemia), and Andreasberg (Harz Mountains). The common arsenic crystal form was mammillary, though a few crude crystals were found.

Examining Arsenopyrite

The primary arsenic mineral is arsenopyrite. The finest arsenopyrite crystals found in recent decades are from the Barroca Grande mine, in Panasquiera, Portugal. This is a source of superb silvery arsenopyrite blades associated with fluorapatite and quartz.

These superb crystals began to appear on the collector market in the early 1960s, and for 10 years, they were recognized as the finest arsenopyrite specimens found in quantity. Typically, the Portuguese arsenopyrite crystals are about an inch long, but exceptional blades several inches long were found on rare occasion. Some showed oscillatory striations across the crystal faces.

Arsenopyrite is an iron arsenic sulfide that develops in hydrothermal deposits, and occasionally even in pegmatites. In Panasquiera, arsenopyrite occurs with superb, zoned, purple fluorapatite crystals and black, striated ferberite that can be several inches long.

All these minerals occurred on fine quartz crystals.

Legendary Locales

The Obira mine, on Kyushu Island, Japan, once yielded fine, small, sharp, silvery crystals that were slightly curved, with a rounded termination. Trepca, Yugoslavia, also produced nice, small arsenopyrites before World War I.

Shortly after that, fine Pansquiera arsenopyrite crystals began coming from the El Tajo mine, in Chihuahua, Mexico. The best reached 2 inches in length, and when they came to grass they were a nice silver color, but they quickly turned gray. The arsenopyrite formed in slightly curved, blunt crystals clustered in subparallel arrangement. The Parral, Chihuahua, arsenopyrites were Mexico’s best, though a mine at Zacetcas did yield some larger crystals, but never in quantity.

The mines of Cornwall are best known for tin and copper. The tin was mined beginning some 3,500 years ago, and perhaps even earlier. What the Greeks, Phoenicians and Romans called the Cassiteride Islands were undoubtedly the British Isles. Tin, or cassiterite, was first sought for use in making bronze. Copper, which came a bit later, became a mainstay of the Cornwall mining industry. A lesser-known metal ore was arsenopyrite, but its impact on the mineral suite of Cornwall cannot be overstated!

The mines of England have long since closed, but the suite of secondary minerals arsenopyite produced due to weathering is still eagerly sought. Arsenopyrite was mined and processed into a white powder of nearly pure arsenic. Imagine handling such a product in the 1800s, when gas masks and proper breathing protection had not yet been invented. To help avoid inhaling the white dust, miners stuffed cotton up their nostrils.

You can guess the results!

Cornish Mine Review

The arsenopyrite in the Cornish mines is important not so much as a sulfide, but for the secondary species it fathered. Weathering of Cornish arsenopyrite produced some of the world’s finest examples of liroconite, olivenite, clinoclase and chacophyllite, all secondary arsenic species.

Of these four, liroconite, a fairly complex hydrous hydrate copper aluminum arsenate, is probably the best known. It is a lovely blue color and was found in small, bright crystals lining cavities. Its primary source was Wheal Gorland. (“Wheal” is the Cornish word for “mine”.) It was also found in Wheal Muttrell and Wheal Tin Tang. Though the mines have been closed for decades, there seems to be a reasonable quantity of liroconite extant, as a specimen or two shows up from old collections regularly.

The world’s finest liroconite specimen has been featured in a number of magazine articles and books. It is a sharp, saillike, 2-inch crystal of excellent color, with light striations. It is part of the Philip Rashleigh collection, which resides in the Royal County Museum at Truro. Rashleigh obtained it in 1811. I have had the privilege of handling the specimen in order to photograph it, at the courtesy of my good friend Courtenay Smale, a Royal County Museum board member.

Aside from the Rashleigh collection, one of the most remarkable and historically important collections in Cornwall resides in Caerhays Castle, near St. Austell, on the south coast. Curated by Courtenay Smale, this collection was described in a superb text by Peter Embrey, then-Curator of Mineralogy, British Museum of Natural History, and R.F. Symes, as being “famous throughout the 19th century”. For decades, the Williams family operated upwards of 22 mines in Cornwall and Devon. Throughout two centuries, they assembled an amazing collection numbering in the tens of thousands of specimens.

When the family acquired Caerhays Castle in the mid-1800s, they invited the School of Mines, Camborne, and the British Museum of Natural History to help themselves to specimens, thus reducing the size of the collection to perhaps a thousand specimens. It is safe to say that these two organizations owe some of their finest Cornwall specimens to the generosity of the Williams family.

Superb Species

The Williams family collection holds 20 or so liroconites, a handful of superb clinoclase specimens—including the finest spherical specimen—a suite of fine olivenite crystal specimens, and several breathtaking chalcophyllite specimens. These superb arsenic species are complemented in the collection by England’s finest torbernite crystals, stunning Chessy azurites, a choice pyrargyrite from Guanajuato, Mexico, and dozens of other superb species.

Olivenite from Cornwall develops in tightly clustered needle-shaped, or acicular, crystals lining cavities. These needles are dark green and have an almost velvety shimmer to them. This mineral was found in several Cornish mines, including Wheal Carrharrack, where the original specimens were found. It also came from Wheal Gorland and Wheal Unity, as well as Tavistock, in nearby Devonshire. Both the Rashleigh and Williams collections have several really choice olivenites.

In this country, fine, small olivenite specimens were found by collectors at Gold Hill, Utah, and Majuba Hill, Nevada. In recent years, some fine specimens have come from the famous Tsumeb mine, in Namibia, Africa.

The Tsumeb olivenite specimens were found in several different forms, all of them very fine. It was found as elongate, small, blocky crystals and as tightly clustered, acicular, dark-green needles. Cap Gronne, France, is well known for a range of minerals, mainly micromount crystals. The olivenite crystals from here are elongate prismatic crystals of fine green color.

Rarity and Relation of Clinoclase and Olivenite

Clinoclase was found in some of the same mines as olivenite. It is a copper hydrous

arsenate, while olivenite’s very similar chemistry has one fewer copper atom. This is because they form in the same environment. Both are monoclinic, but clinoclase can be tabular, in crystals that sometimes form pseudohexagonal crystals. Much more common are needles of clinoclase, which develop in tight, radiating groups that form as fans and sometimes in complete spherules. When these radiating spherules are broken, the fan arrangement of the needles is very obvious. The color of clinoclase needle clusters is dark green, but they can be so dark as to appear blue-black.

Some of the most attractive and classic examples of clinoclase are found in the Williams collection, housed at Caerhays Castle. The finest of these is a 3-inch-diameter specimen that developed in a complete, smooth-surfaced spherule of radiating needles. This specimen is generally considered the world’s finest by collectors who know Cornwall species very well.

Of all the secondary arsenic species from Cornwall, the most beautiful is chalcophyllite.

In my opinion, it actually exceeds the complex copper, aluminum arsenate hydrous hydrate liroconite. While liroconite is a lovely blue mineral in well-crystallized prisms, chalcophyllite glistens with a lovely greenish-blue color, and occurs in platy, aggregate, hexagonal crystals in superb micaceous clusters. It flashes with a very attractive pearly luster, which enhances the overall appearance of the small crystals. The crystals are never large—seldom more than a few millimeters across—but clusters of them line cavities in matrix and sparkle beautifully. Their sparkly luster and rich color and attractive crystal clusters really make chalcophyllite one of the more appealing, most attractive copper arsenates found in Cornwall. Some chalcophyllite crystals are quite dull and tend to be a pale, cloudy, greenish-blue color, and have been shown to be altered to chrysocolla.

Appreciating Scarce Minerals

The mines of Cornwall that yielded chalcophyllite include Wheal Gorland and Wheal Unity. These two mines often produced the same suite of species, since they actually exploited the same ore vein, or lode. Wheal Ting Tang, as well as mines in St. Day and Redruth, also produced fine chalcophyllite crystals.

Unfortunately, the arsenic minerals from Cornwall have long since disappeared from the market. Once in a while, a liroconite shows up from an old collection, but they are seldom seen otherwise. The same is true of native arsenic, which showed up sparingly in some of the silver mines of Germany and Czechoslovakia.

Fortunately, small examples of some of the arsenic species have been found at Majuba Hill and Gold Hill, favorite collecting sites for Western collectors. Tsumeb is now closed, so arsenic species from that mine are eagerly sought, but seldom offered for sale.

The post Arsenic Family Minerals Part I: Liroconite, Clinoclase, Olivenite and Chalcophyllite first appeared on Rock & Gem Magazine.