Poisonous Rocks and Minerals of the World

Poisonous Rocks and Minerals of the World

We often wonder if the Earth beneath our feet could swallow us up. The truth is more insidious. Drop that rock you just picked up . . . you could get poisoned.

This post details the ten most toxic and potentially deadly minerals that crystalize in the Earth’s rocks, presenting a dangerously deceptive array of stony beauty. These rocks don’t have to be thrown to hurt you.

It’s easy to forget how lethal our natural world can be, where an encounter with the wrong rock or mineral could lead to injury or death. Often times toxic minerals are associated material we use everyday for construction, computers, and cosmetics. With a keen eye and an understanding of toxicity, you can help to identify deadly minerals in your surrounding.


Coloradoite is a recently discovered crystalline mineral originating in magma veins. The mineral is a mercury telluride compound formed when mercury fuses with tellurium, another extremely toxic and rare metal. Coloradoite therefore poses a doubly toxic threat to anyone daring to handle it. The combination of the two elements poses the risk of serious poisoning if carelessly handled. If heated or chemically altered, deadly vapor and dust is released by this strange mineral. Interestingly, the mineral may be mined for its tellurium content. Tellurium minerals may combine with gold, but were previously not recognized. In a strange twist of fate, the streets of Kalgoorie in Australia were mined in a bizarre gold rush after the realization that gold-bearing Tellurides had been used to fill potholes.

More Chemistry: Coloradoite, also known as mercury telluride (HgTe), is a rare telluride ore associated with metallic deposit (especially gold and silver). Gold usually occurs within tellurides, such as coloradoite, as a high-finess native metal.

The quest for mining led to the discovery of telluride ores which were found to be associated with metals. Tellurides are ingrown into ores containing these precious metals and are also responsible for a significant amount of these metals being produced. Coloradoite, a member of the coordination subclass of tellurides, is a covalent compound that is isostructural with sphalerite (ZnS).Its chemical properties are highly instrumental in distinguishing it from other tellurides. It was first discovered in Colorado in 1877. Since then, other deposits have been found. Although it plays an important role in the geology of minerals, it can also be used for other purposes.

Telluride ores occur mainly with metal deposits. In 1848, C.T. Jackson was the first to discover an American mineral containing the element tellurium in the Whitehall mine, in Spotsylvania County, near Fredericksburg, Virginia. Tellurides of gold were first discovered in 1782 in Transylvania and subsequently other telluride ores were found in other parts of the world (Mark and Scibird, 1908). The first discovery and description of coloradoite was by Frederick Augustus Genth in the Boulder veins of Colorado in 1877 and so named after the place of discovery. Other studies have reported its occurrence in other mines of the region and also in mines of the world’s significant telluride locations. First classified in the 02 class of minerals by James Dana, its classification number is It is also has a Strunz classification of 02.CB.05a, as a metal sulfide with gold, silver, iron, copper and other metals.


Seductive blue chalcanthite crystals are composed of copper, combined with sulfur and other elements and water. This arrangement turns copper, which is required by the body but toxic in excess quantities, into an extremely bio-available crystal. In another words, the copper becomes water soluble, and may be assimilated in great quantities by any plant or animal, rapidly weakening it and then killing it by shutting down body processes. Chalcanthite should never be taste tested by amateur scientists for salt content, or an extremely serious overdose of copper could result. Just releasing crystals of the blue mineral has killed entire ponds of algae, and posed great environmental threats. Because of the incredible beauty and rarity of chalcanthite, an enterprise dedicated to growing artificial crystals and passing them off as genuine specimens for sale has developed within the geological community.

More Chemistry: Chalcanthite, whose name derives from the Greek, chalkos and anthos, meaning copper flower, is a richly colored blue/green water-soluble sulfate mineral CuSO4·5H2O. It is commonly found in the late-stage oxidation zones of copper deposits. Due to its ready solubility, chalcanthite is more common in arid regions.

Chalcanthite is a pentahydrate and the most common member of a group of similar hydrated sulfates, the chalcanthite group. These other sulfates are identical in chemical composition to chalcanthite, with the exception of replacement of the copper ion by either manganese as jokokuite, iron as siderotil, or magnesium as pentahydrite.

Other names include blue stone, blue vitriol, and copper vitriol.

As chalcanthite is a copper mineral, it can be used as an ore of copper. However, its ready solubility in water means that it tends to crystallize, dissolve, and recrystallize as crusts over any mine surface in more humid regions. Therefore, chalcanthite is only found in the most arid regions in sufficiently large quantities for use as an ore.

Secondarily, chalcanthite, due to its rich color and beautiful crystals, is a sought after collector’s mineral. However, as with its viability as an ore, the solubility of the mineral causes significant problems. First, the mineral readily absorbs and releases its water content, which, over time, leads to a disintegration of the crystal structure, destroying even the finest specimens. It is critical to store specimens properly to limit exposure to humidity. Second, higher quality crystals can be easily grown synthetically, and, as such, there is a concern that disreputable mineral dealers would present a sample as natural when it is not.


Thallium is the dark twin of lead. This thick, greasy metal is similar in atomic mass but even more deadly. Thallium is a rare metal that appears in highly toxic compounds consisting of rather strange combinations of elements. The effects of thallium exposure are even more peculiar, and include loss of hair, serious illness through skin contact and in many cases, death. Hutchinsonite is a hazardous but dramatic mixture of thallium, lead and arsenic. The three poisonous metals form a lethal mineral cocktail that should be handled only with great caution. Hutchinsonite was named after John Hutchinson, a prominent mineralogist from Cambridge University. The mineral is found in mountainous regions of Europe, most frequently in ore deposits.

More Chemistry: Hutchinsonite is a sulfosalt mineral of thallium, arsenic and lead with formula (Tl,Pb)2As5S9. Hutchinsonite is a rare hydrothermal mineral.

It was first discovered in Binnental, Switzerland in 1904 and named after Cambridge mineralogist Arthur Hutchinson, F.R.S. (1866–1937).


Galena is the principle ore of lead, and forms glistening silver cubes with almost unnaturally perfect shapes. Although lead is normally extremely flexible, the sulfur content of galena makes it extraordinarily brittle and reactive to chemical treatment. Galena is capable of taking an equally heavy toll on workers and amateur researchers who are exposed to it. Contact with specimens may lead to lead dust exposure, while workers in mines face a high risk of poisoning from contact with the mineral and the deadly dusts released through production. Once extracted, the lead content from this mineral poses environmental and health threats during treatment and extraction. Galena has a cubic fracture, and if hit with a hammer, the crystal will shatter into multiple smaller replicas of its original shape.

More Chemistry: Galena PbS, also called lead glance, is the natural mineral form of lead (II) sulfide. It is the most important ore of lead and an important source of silver.

Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms. It is often associated with the minerals sphalerite, calcite and fluorite.

One of the oldest uses of galena was in the eye cosmetic kohl. In Ancient Egypt, this was applied around the eyes to reduce the glare of the desert sun and to repel flies, which were a potential source of disease.

Galena is the primary ore of lead, which is mainly used in making lead–acid batteries; however, significant amounts are also used to make lead sheeting and lead shot. Galena is often mined for its silver content, such as at the Galena Mine in northern Idaho.

Also known as “potter’s ore”, galena is used in a green glaze applied to pottery. Galena is a semiconductor with a small band gap of about 0.4 eV, which found use in early wireless communication systems. It was used as the crystal in crystal radio receivers, in which it was used as a point-contact diode capable of rectifying alternating current to detect the radio signals. The galena crystal was used with a sharp wire, known as a “cat’s whisker” in contact with it. The operation of the radio required that the point of contact on the galena be shifted about to find a part of the crystal that acted as a rectifying diode. Making such wireless receivers was a popular home hobby in Britain and other European countries during the 1930s. Scientists associated with the investigation of the diode effect are Karl Ferdinand Braun and Jagadish Bose. In modern wireless communication systems, galena detectors have been replaced by more reliable semiconductor devices.


Chrysotile and Amphibolite

Asbestos is not a manmade product, but one of most terrifying minerals on the planet. Where other minerals act as toxins through their chemistry and sicken victims of accidental poisoning, Asbestos conducts full scale mechanical sabotage on the human lung. Asbestos is a fully natural category of minerals composed of silica the most abundant of Earth’s hard elements, iron, sodium and oxygen. Asbestos deposits consist of aggregates of thousands of tiny, fibrous crystals that can become airborne and lodged in the human lung. Carcinogenic effects occur through persistent irritation of the lung tissues, leading to scarring. Asbestos formations can also be uncovered among any set of silica rocks, warranting caution when exploring. Strangely, natural weathering leads to natural distribution of asbestos in Earth’s atmosphere. As a result, many humans carry some asbestos fibers in their lungs.

More Chemistry: Asbestos Mg3Si2O5(OH)4 is a set of six naturally occurring silicate minerals, which all have in common their asbestiform habit: i.e., long (roughly 1:20 aspect ratio), thin fibrous crystals, with each visible fiber composed of millions of microscopic “fibrils” that can be released by abrasion and other processes. The minerals are chrysotile, amosite, crocidolite, tremolite, anthophyllite, and actinolite.

Asbestos has been mined for over 4,000 years, but large-scale mining began at the end of the 19th century, when manufacturers and builders began using asbestos for its desirable physical properties. Some of those properties are sound absorption, average tensile strength, affordability, and resistance to fire, heat, and electricity. It was used in such applications as electrical insulation for hotplate wiring and in building insulation. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement or woven into fabric or mats. These desirable properties led to asbestos being used very widely until the late 20th century.

Inhalation of asbestos fibers can cause serious and fatal illnesses including lung cancer, mesothelioma, and asbestosis (a type of pneumoconiosis).Asbestos is currently estimated to cause 255,000 deaths per year. Concern for asbestos-related illness began in the 20th century and escalated during the 1920s and 1930s. By the 1980s and 1990s, asbestos trade and use were heavily restricted, phased out, or banned outright in an increasing number of countries. Many developing countries still support the use of asbestos as a building material, and mining of asbestos is ongoing, with the top producer Russia producing around one million metric tonnes in 2015.

Despite the severity of asbestos-related diseases, the material has extremely widespread use in many areas. Continuing long-term use of asbestos after harmful health effects were known or suspected, and the slow emergence of symptoms decades after exposure ceased, made asbestos litigation the longest, most expensive mass tort in U.S. history though a much lesser legal issue in most other countries involved. Asbestos-related liability also remains an ongoing concern for many manufacturers, insurers and reinsurers.


Arsenopyrite is fool’s gold, but with a difference. One would not just be a fool to mistake it for gold. Equally foolish would be a decision to pick up this mineral on a hike at a quarry, and proceed to use your hands to put trail mix in your mouth. Arsenopyrite is arsenic iron sulfide, which is the same type of mineral as pyrite (fool’s gold, iron sulfide), but with a heavy addition of arsenic. If one attempts to heat or in any way alter the mineral, a strong garlic odor of arsenic will be produced as lethally toxic, corrosive and carcinogenic vapors are released. Just handling the mineral brings one into contact with unstable sulfuric arsenic salts. Interestingly, arsenopyrite may be identified by striking a specimen with a hammer. The powerful garlic odor of arsenic can be briefly detected as the sparks fly.

More Chemistry: Arsenopyrite is an iron arsenic sulfide (FeAsS). It is a hard (Mohs 5.5-6) metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1. When dissolved in nitric acid, it releases elemental sulfur. When arsenopyrite is heated, it produces poisonous sulfur and arsenic fumes which can be fatal if inhaled in large quantities. With 46% arsenic content, arsenopyrite, along with orpiment, is a principal ore of arsenic. When deposits of arsenopyrite become exposed to the atmosphere, the mineral will slowly oxidize, converting the arsenopyrite into an iron arsenate, a relatively stable compound. Arsenopyrite is generally an acid consuming sulfide mineral unlike iron pyrite which can lead to acid mine drainage.

The crystal habit, hardness, density, and garlic odor when struck are diagnostic. Arsenopyrite in older literature may be referred to as mispickel, a name of German origin.

Arsenopyrite also can be associated with significant amounts of gold. Consequently, it serves as an indicator of gold bearing reefs. Many arsenopyrite gold ores are refractory, i.e. the gold is not easily cyanide leached from the mineral matrix.

Arsenopyrite is found in high temperature hydrothermal veins, in pegmatites, and in areas of contact metamorphism or metasomatism.


Torbernite is the mineral from hell. The prism shaped green crystals form as secondary deposits in granitic rocks, and are composed of uranium. Formed through a complex reaction between phosphorous, copper, water and uranium, the stunning crystal displays have seduced many mineral collectors into taking a sample for a shelf collection. If the uranium decay from a pocket sized Chernobyl were not enough, lethal radon gas capable of causing lung cancer slowly releases from these hot rocks. This is one crystal to leave alone. Torbernite can occur in granite, so your stone countertop just might contain traces of torbernite. The bright green crystal blooms were used by prospectors as indicators of uranium deposits.

More Chemistry: Torbernite, whose name derives from the Swedish chemist Torbern Bergman (1735–1784), is a radioactive, hydrated green copper uranyl phosphate mineral, found in granites and other uranium-bearing deposits as a secondary mineral. Torbernite is isostructural with the related uranium mineral, autunite.

The chemical formula of torbernite is similar to that of autunite in which a Cu2+cation replaces a Ca2+. The number of water hydration molecules can vary between 12 and 8, giving rise to the variety of metatorbernite when torbernite spontaneously dehydrates. Their respective chemical compositions are the following:

Torbernite:  Cu(UO2)2(PO4)2 • 12H2O

Metatorbernite: Cu(UO2)2(PO4)2 • 8H2O

Torbernite’s most common alternative names are copper uranite and cupro-uranite.

As a radioactive mineral, torbernite has some limited significance as a uranium ore. Its vibrant green color and well-developed distinctive crystals (size: mm to a few cm) make it a sought-after collector’s mineral, as well. However, torbernite, like other hydrated minerals, can easily suffer from loss of water molecules. This loss of water from the mineral leads to an alteration of torbernite specimens into its pseudomorph, meta-torbernite. Some collector’s websites assert that any torbernite specimen more than a few years old should be considered fully transitioned to meta-torbernite. However, it likely depends on the temperature and relative humidity of ambient air in which specimens are stored.

As torbernite is radioactive and outgases radon (222Rn), collectors are urged to take proper precautions in the handling and storage of any specimens. An adequate ventilation of the rooms and the cabinets in which the specimens are stored is essential to evacuate the radioactive radon gas responsible for lung cancer, but it could increase the dehydration rate of the specimens. To limit radon inhalation, naked specimens should never be stored in rooms in which one spends much living or working time. An alternative is to store specimens in gas tight transparent containers in which radon will accumulate and decay to secular equilibrium.


Stibnite is antimony sulfide, but it looks like silver. For that reason, the huge, shining metallic crystals of this unstable compound were once fashioned into magnificent eating utensils. But the sword shaped crystals bore the powers of death to those who used them. Stibnite’s antimony laced crystals killed a number of people before it became known that use of the mineral was causing food poisoning of the worst kind. Even in collections, stibnite samples should be handled with great caution to avoid poisoning. Hand washing is advisable after any contact. Mines near Oksaku in Japan have produced the best stibnite crystals in the world, measuring up to a foot in length. Many stibnite samples have the appearance of a miniature steeple.

More Chemistry: Stibnite, sometimes called antimonite, is a sulfide mineral with the formula Sb2S3. This soft grey material crystallizes in an orthorhombic space group. It is the most important source for the metalloid antimony. The name is from the Greek στίβι stibi through the Latin stibium as the old name for the mineral and the element antimony.

Pastes of Sb2S3 powder in fat or in other materials have been used since ca. 3000 BC as eye cosmetics in the Middle East and farther afield; in this use, Sb2S3 is called kohl. It was used to darken the brows and lashes, or to draw a line around the perimeter of the eye.

Antimony trisulfide finds use in pyrotechnic compositions, namely in the glitter and fountain mixtures. Needle-like crystals, “Chinese Needle”, are used in glitter compositions and white pyrotechnic stars. The “Dark Pyro” version is used in flash powders to increase their sensitivity and sharpen their report. It is also a component of modern safety matches. It was formerly used in flash compositions, but its use was abandoned due to toxicity and sensitivity to static electricity.

Stibnite was used ever since protodynastic Ancient Egypt as a medication and a cosmetic. The Sunan Abi Dawood reports, “prophet Muhammad said: ‘Among the best types of collyrium is antimony (ithmid) for it clears the vision and makes the hair sprout.’”

The 17th century alchemist Eirenaeus Philalethes, also known as George Starkey, describes stibnite in his alchemical commentary An Exposition upon Sir George Ripley’s Epistle. Starkey used stibnite as a precursor to philosophical mercury, which was itself a hypothetical precursor to the Philosopher’s stone.


The only thing worse than arsenic itself could be a rock made from arsenic and sulfur. The lethal and chemically reactive orpiment crystals are found growing below the surface in mineral formations, often near hydrothermal vents. The colors are seductive, but holding the crystals in your hands may release carcinogenic, neurotoxic arsenic powder. Like cinnabar, the Chinese made extensive use of this mineral, but to far more terrifying ends. Arrows would be rubbed on crushed samples of these stones and then launched to poison the enemy in a rather fancy way to throw a rock. Orpiment is known to give off a strong garlic smell due to its arsenic content, and may crumble into dangerous powder when exposed to light. The mineral was used as a primary component of ochre paint, and likely poisoned many of the artists who used it.

More Chemistry: Orpiment  As2S3 was traded in the Roman Empire and was used as a medicine in China, even though it is very toxic. It has been used as fly poison and to tip arrows with poison. Because of its striking color, it was of interest to alchemists, both in China and the West, searching for a way to make gold.

For centuries, orpiment was ground down and used as a pigment in painting and for sealing wax, and was even used in ancient China as a correction fluid. It was one of the few clear, bright-yellow pigments available to artists until the 19th century. However, its extreme toxicity and incompatibility with other common pigments, including lead and copper-based substances such as verdigris and azurite, meant that its use as a pigment ended when cadmium yellows, chromium yellows and organic dye-based colors were introduced during the 19th century.

Orpiment is mentioned in the 17th century by Robert Hooke in Micrographia for the manufacture of small shot.

Orpiment is used in the production of infrared-transmitting glass, oil cloth, linoleum, semiconductors, photoconductors, pigments, and fireworks. Mixed with two parts of slaked lime, orpiment is still commonly used in rural India as a depilatory. It is used in the tanning industry to remove hair from hides.


Cinnabar (mercury sulfide) is the single most toxic mineral to handle on Earth. The name of the crystal means dragons blood, and it is the main ore of mercury. Forming near volcanos and sulfur deposits, the bright red crystals signal danger of the worst kind. Cinnabar may release pure mercury if disturbed or heated, causing tremors, loss of sensation and death. In the Middle Ages and late 1700s, being sent to work in Spanish mines containing cinnabar formations was widely considered a death sentence. Cinnabar was widely used in Chinese history for ornamental food dishes, and intricate carvings were created from chunks of it, sometimes at the expense of the artisans. Even more incredibly, some ancient medical practitioners believed cinnabar held healing powers, and prescribed it for certain conditions.

More Chemistry: Cinnabar and cinnabarite, likely deriving from the Ancient Greek: κιννάβαρι (kinnabari), refer to the common bright scarlet to brick-red form of mercury (II) sulfide (HgS) that is the most common source ore for refining elemental mercury, and is the historic source for the brilliant red or scarlet pigment termed vermilion and associated red mercury pigments.

Cinnabar generally occurs as a vein-filling mineral associated with recent volcanic activity and alkaline hot springs. The mineral resembles quartz in symmetry and in its exhibiting birefringence; cinnabar has a mean refractive index of approximately 3.2, a hardness between 2.0 and 2.5, and a specific gravity of approximately 8.1. The color and properties derive from a structure that is a hexagonal crystalline lattice belonging to the trigonal crystal system, crystals that sometimes exhibit twinning.

Cinnabar has been used for its color since antiquity in the Near East, including as a rouge-type cosmetic, in the New World since the Olmec culture, and in China since as early as the Yangshao culture, where it was used in coloring stoneware.

Associated modern precautions for use and handling of cinnabar arise from the toxicity of the mercury component, which was recognized as early as ancient Rome.



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