Charoite is a rare

silicate mineral Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

, first described in 1978. It was believed to be named after the

Chara River , image = 2000 Charoite 613.jpg , image_size = , image_caption = View of the river and piece of charoite , pushpin_map = Russia Sakha Republic , pushpin_map_size = , pushpin_map_caption= Location ...

, but due to the river being 70 km away from its discovery place, now it is believed to be named after the Russian word ''chary'', meaning magic or charms. When it was discovered, it was thought to be a fake, dyed purple to give it its striking appearance.

Properties

Charoite is translucent lavender to purple in color with a pearly luster. Charoite is strictly massive in nature, and fractures are

conchoidal Conchoidal fracture describes the way that brittle materials break or fracture when they do not follow any natural planes of separation. Mindat.org defines conchoidal fracture as follows: "a fracture with smooth, curved surfaces, typically sli ...

. It has an unusual swirling, fibrous appearance, sometimes

chatoyant In gemology, chatoyancy ( ), or chatoyance or cat's eye effect, is an optical reflectance effect seen in certain gemstones, woods, and carbon fibre. Coined from the French "œil de chat", meaning "cat's eye", chatoyancy arises either from the ...

, and that, along with its intense color, can lead many to believe at first that it is synthetic or enhanced artificially. Though reportedly discovered in the 1940s, it was not known to most of the world until its description in 1978. It is said to be opaque and unattractive when found in the field; a fact that may have contributed to its late recognition. Charoite consists of oxygen (43.75%), silicon (27.65%) and calcium (17.53%) mainly, but its composition includes potassium (10.69%) - which gives it its radioactive properties - and hydrogen (0.39%) as well. It has a barely detectable, 0.65% radioactivity concentration per

Gamma Ray American Petroleum Institute Units Gamma (uppercase , lowercase ; ''gámma'') is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter re ...

. Inclusions mainly come in the swirly patterns of the mineral. The black spots on some specimens are either

augite Augite is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees. Characteristics Augite is a solid solution in the pyroxene group. ...

aegirine Aegirine is a member of the clino pyroxene group of inosilicate minerals. Aegirine is the sodium endmember of the aegirine- augite series. Aegirine has the chemical formula Na Fe Si2 O6 in which the iron is present as Fe3+. In the aegirine-augit ...

, the latter occurring in almost all charoites since they commonly grow together. Larger round greenish spots are

feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...

. Lighter colored stones or ones with translucent areas are likely due to canasite. The yellowish brown spots are

tinaksite Tinaksite (chemical formula ) is a mineral found in northern Russia. Tinaksite can be grayish-white, yellowish, orange, or brown, and it is often found in charoite Charoite is a rare silicate mineral, first described in 1978. It was believed to ...

, which was discovered at the same time as charoite was. Charoite's silky, fibrous structure results in a shimmery looking polished stone. Sometimes, the very white flashes are tiny white feldspar.

Sugilite Sugilite ( ) is a relatively rare pink to purple cyclosilicate mineral with the complex chemical formula K Na2( Fe, Mn, Al)2 Li3 Si12 O30. Sugilite crystallizes in the hexagonal system with prismatic crystals. The crystals are rarely found and ...

s and charoites can be confused, as both are purple, and sugilite can have black and white inclusions, however sugilite lacks the swirling pattern that are present in charoite stones, and it also lacks the chatoyant effect.

Occurrences

It has been reported only from the

Aldan Shield Aldan Shield (russian: Алданский щит) is a shield in Siberia. It is an exposed basement of the Siberian Craton. Together with the Anabar Shield further to the northwest, the Aldan Shield is one of the main features of the craton. T ...

Sakha Republic Sakha, officially the Republic of Sakha (Yakutia),, is the largest republic of Russia, located in the Russian Far East, along the Arctic Ocean, with a population of roughly 1 million. Sakha comprises half of the area of its governing Far Eas ...

, Siberia, Russia. It is found where a

syenite Syenite is a coarse-grained intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, if present at all, occurs in relatively small concentrations (< 5%). Some syenites contain larger proport ...

of the

Murun Massif Murun (russian: Мурун) is a mountain in the Olyokma-Chara Plateau, at the border of Irkutsk Oblast and Yakutia, Russian Federation. Geography A high summit is the highest point of the Murun Massif in the Olyokma-Chara Plateau, part of th ...

has intruded into and altered

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

deposits producing a

potassium feldspar Potassium feldspar refers to a number of minerals in the feldspar group, and containing potassium: *Orthoclase (endmember formula K Al Si3 O8), an important tectosilicate mineral that forms igneous rock *Microcline, chemically the same as orthoclas ...

metasomatite, and forms between 200 - 250 °C. Tinaksite, canasite and charoite are associated and black aegirine is also common where these three minerals grow. Common impurities include

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

strontium Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...

and

barium Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

. Charoitite is a rock like lapis lazuli, but unlike the latter one, charoitite mostly consists of the mineral charoite.

Marketing and Uses

When it arrived to the western market, it was already named charoite. Common tradenames include charoite jade and lilac stone. Although considering its rarity and only type locality, even the highest quality charoite gemstones cost only a few dollars a carat, usually costing between 1.10 - $3 per carat. In its price, color and chatoyancy are the main factors. Chatoyant translucent varieties are the most sought after, as while chatoyancy already being uncommon in the mineral, translucent varieties are rarer than the more common opaque ones. Amongside jewelry, due to the fact that the material can be massive in size, charoite can be used in the making of bookends, vases, goblets, boxes, or in small statues. Although its relatively high hardness, it makes poor center pieces in rings and in bracelets. As it is a heat sensitive mineral, the mechanical cleaning of it should be avoided. It is recommended to use mild detergents and soft brushes or a cloth to clean it, and to never use strong and toxic detergents on it.

Gallery

Charoitite, sw Yakutia Siberia.jpg, Charoitite, a charoite-dominated potassic metasomatite rock from the type area. Photo is 5.7 cm wide. 2000 Charoite 613.jpg, Charoite postage stamp, 2000, from a series commemorating "300 Years of Mining and Geological Service in Russia."

References

{{Gemstones Calcium minerals Sodium minerals Potassium minerals Inosilicates Monoclinic minerals Minerals in space group 11