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Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

GYPSUM, GROUP: GYPSUM, ANHYDRITE


GYPSUM group (Gips—Gypse—√ипс) (Teophrastus, 315 BC) from Gk. “gypsos” – plaster, alluding to its principal use. Known from the antiquity.

Composition & Properties. Sulfate group – Ca[SO4]·2H2O, monoclinic system. Hardness 2. Density 2.3. Glass luster, silk one in fibrous aggregates. Perfect cleavage in one direction. Fragile. Under the general name gypsum, three materials are described: 1) mineral gypsum; 2) rock composed with it; and 3) artificial product of annealing of gypsum. Besides, a water-free analogue of gypsum is described here – anhydrite. It is also an ornamental stone.

1. Gypsum – mineral is found as lamellar, columnar and needle crystals and parallel-fibrous aggregates. Color: colorless and transparent, also white, gray, pale blue, greenish, yellow, orange to brownish. Transparent to translucent. A lamellar glassy variety with pearl play of color on the cleavage planes is known under the name of Maria glass. The origin of this name is connected with the fact, that they framed images of the Virgin Mary with the thinnest plates of gypsum in the ancient times. That’s why it is also called maiden ice, or Lady’s ice. Till the end of the 19th cent., this variety of gypsum was known as selenite. However, since 1876, after the foundation of the stone-carving manufactures in the Urals, the name selenite has been used in Russia for a fibrous variety of gypsum. So, this stone was connected with the Moon to attracted buyers. Silk play of color in selenite and pearl glistening of the “Moon strip”, which is moving on the polished surface of a cabochon, explained it. From fibrous gypsum they cut small stone-carving work of art, balls and other figures. From that time on, the name selenite was fixed with this variety of gypsum. Parallel-fibrous aggregates of satin gypsum display the effect of cat’s-eye on the polished, roundest surface – gypsum cat’s-eye. In crystals of gypsum, there are often different inclusions, which sometimes form a pattern of “sand-glass”.

Deposits. Accumulations of gypsum are linked with sea-shoal deposits, which are widely represented at all the continent of the world (See gypsum 2 – rock). Besides, it is formed in the weathering zones, in the process of metasomatism and at some hydrothermal deposits. Large crystals of gypsum were found at many deposits through all the world. Interesting collection samples are druses of its crystals – gypseux rose. Sometimes, such clusters are overcrowded with sandy-grains with the admixture of iron combinations; they are called sand’s rose, or desert rose. In Russia gypsum roses are known in the low reaches of the Volga River, at the Baskunchak Lake deposit, and also in the South Urals, at the Gaiskoye deposit and others. In Turkmenistan, at the Gaurdak deposit, they found crystals of gypsum up to 15 cm. long, enriched with inclusions of sulfur. Such deposits are also in Iran; crystals reach 30 cm. there. In Romania, gypsum is represented with transparent columnar crystals up to 76x23x10 cm. at the Cavnic (form. Kapnik) deposit. In Poland, at the Machów deposit, to the southwest from Tarnobrzeg, the size of its crystals reached 4 m. In Slovakia, at the deposits Banská Štiavnica, Kremnica, Novoveská Huta and others they discovered both crystals of gypsum and its lamellar variety of Maria glass, gypsum rose and alabaster. In Algeria, in the Sahara Desert, gypsum roses are found especially often by Oued-es-—оурег. In Australia, in Queensland, to the south from Cloncurry, at the Mt. Elliott mine, they found crystals of gypsum up to 1 m. long. In the U.S.A., at the Lechagilla deposit, New Mexico, they also found large crystals of gypsum. But the biggest ones were found in Mexico. There, at the deposits Maravillas, Gibraltar and Francisco Portillo, Chihuahua State, they found crystals up to 12 m. long. In Chile, crystals of gypsum reached 3 m. long at the Braden mine and especially at the El Teniente, Santiago region.

Synonyms. Atlasgips, Germ. | Chimaltizatl, local Aztec name for selenite | Russian crystal, obs. | Fasergips, Germ. | Fibrolite | Fraueneis, Germ. | Ass mirror | Selenite, from Gk. “Selena” – the Moon | Sericolite, from Gk. “serikos” – silky in fibrous aggregates, because of their luster, obs. | ~ Spar: cat’s ~, gypsum ~, mirror ~, Niagara ~, after the Locklort deposit in the U.S.A., near Niagara, New York State; satin ~, silk ~ | Gypsum stone | Mirror stone | Satin stone | Zelenit, obs. | Zerkalik (from mirror), Old Russ.

Treatment. Parallel-fibrous aggregates of gypsum – selenite are used mainly as non-expensive ornamental stone. Stone-carving souvenirs from selenite have been a traditional trade of many peoples since the ancient times. In Russia, this trade was developed in the Urals, near Kungur and in other regions by 1820. Carved work of art from selenite from Urals are known, a popular form was egg-shaped, and such objects were frequently given as Easter gifts. In the State Hermitage, SPb., there is a vase from selenite, 35 cm. high and 49 cm. in diameter. Domestic craft in producing different work, of art from selenite exists in Peru, but the mot popular in the world are carved things from translucent selenite from the region of Volterra, Italy.

2. Gypsum – ornamental rock, composed mainly with cryptocrystalline gypsum is used to be called alabaster. Different mineral admixtures can be in its content. Usually there are such admixtures in alabaster as anhydrite, dolomite, calcite, celestine and clay minerals. According the content, varieties of this rock are gypsum-anhydrite and gypsum-dolomite. The structure of the rock is massive, paurograined. Its color is mainly light: snow-white, gray, honey-yellow, rose-brownish, rarely violet and black, with spotty or micro corrugated texture. This rock is non-transparent to translucent, sometimes with glass luster – glass alabaster. Alabaster looks like marble; and for long the both of them have been treated as calcareous earth. Only in 1746, they established that alabaster and limestone are composed with different minerals.

Deposits. Thick layers of gypsums were formed as a result of chemical genesis at the sea-shoal and in salt lakes in the ancient epochs of the history of the Earth. In Russia, there are significant resources of alabaster in different regions. The biggest concentration of them is in the northwest of Russia – in the Arkhangel’sk and Pskov Regions; and also in the central part of the country – in the Nizhniy Nowgorod and Tula Regions; and in the region of Volga – in the Autonomus Republics Mary El, Tatarstan and in the Samara Region. In the Northern Caucasus, they exploit deposits of alabaster, sometimes with selenite, in the Stavropol’ Region and Krasnodar Region and Dagestan. In the Urals, deposits of alabaster are registered along all the western slope of the Rep. of Komi – in the north; at the Kungur deposit in the Perm’ Region and up to Sol Iletskoye deposit in the Orenburg Region – in the south. In East Siberia, deposits of alabaster are at the Altai, in the Krasnoyarsk Region and the Irkutsk Regions.

Because deposits of alabaster are widespread in many countries of the world, we will mention only unusual types of them. In hydrothermal veins of Tadzhikistan, at the Pamirs Mts., they discovered a violet variety of radioanhydrite with radioactive admixtures. In Europe, the most significant deposits of alabaster are situated in Austria – near Salzburg, in Poland – in the regions of Rybnik and Velichka in Wojewodztwo Slaskie (Lower Silesia); and in Italy – in the region of Volterra.

Synonyms. Alabaster (alabastrum, alabastrite), after Alabastron in Egypt, the place of manufacturing and trade of goods from this material | ~ alabaster: agate ~, amber ~, gypsum ~, mirror ~, serpentine ~, specular ~, pink Welsh ~, rose, stripy, from Glamorgan, Wales, England | Kremennic, obs. | Ledenez, obs. | Bergamo marble | Oldendorf marble | Zhigulevskiy marble | Marmolite | Curly stone, from it’s aggregates | Ribbon stone.

Treatment. Alabaster, as well as anhydrite, is classified as a soft ornamental stone, it is easy processed, polished; it display ornamental properties. In Ancient Egypt, it was used as an ornamental stone in 4500 B.C. Oil vessels, made from this material were called “alabastres”. In the Museum of Fine Arts in Moscow, an Egyptian narrow-necked vase is exhibited, about 1 m. high, made in the antique times. Such vases with sources of light inside them served as lamps. Alabaster lamps are in the Gatchina Palace by St Petersburg, they were also in the hotel “Moscow” in Moscow. In the 16-17th cent., in Europe, Ital., carved products from translucent alabaster from the Volterra, Tuscany Prov. came in fashion. The upper point of the craft of Tuscan masters was a carved copy of the Milan Cathedral made from alabaster in 1/50 of the real size, which was exhibited at the World Exhibition in London in 1862. The trade of carved producing from alabaster is flourishing in Italy in Bergamo, Lombardy, where there are deposits of Bergamo marble. In Germany, such craft was developed in Lower Saxony thanks to the findings of Oldendorf marble at the Harz Mts. In Russia, a similar center of processing of anhydrite is the Kungur Dist., Perm’ Region. There a craft of carving from alabaster has been existing for a hundred of years. A similar center is in the region of Volga, in the Samara Region, where alabaster is extracted as Zhigulevskiy marble. Since 1952, in Arkhangel’sk they opened a lapidary manufacture of producing from gypsum and anhydrite. Such centers of gypsum processing are in the south of Russia. Carved goods from alabaster are stabilized after producing, which make them especially white and harder.

Legends. White alabaster is a talisman of purity and innocence. As an amulet, it protected against cold and diseases of spleen.

Similarity. Gypsum resembles calcite, from which it differs with lower hardness, cleavage in one direction and the absence of the reaction with hydro-chlorine acid.

3. Gypsum – product of annealing. Partly dehydrated through heating and grinded into powder gypsum in composition with water becomes solid, stone-like mass. That’s why it has been used as construction material since the deepest antiquity. It is used for manufacturing of artificial marble – shtück, for casting of architectural details, for funeral masks, for copying of sculpture and small stone carving. To make casts warmer, Ital. masters covered them with wax and then polished their surface.

Anhydrite (Anhydrit—Anhydrite—јнгидрит) (Poda, 1794 in Ludwig, C.F., 1804), from Gk. “anhydrous” – water-free, after the content. Composition – Ca[SO4], orthorhombic analogue of gypsum. Hardness 3.5-4. Density 2.8-3. Glass luster. Perfect cleavage in three directions. It differs from gypsum with the cleavage in three directions in crystals. It is a rock-forming mineral for the ornamental stone with the same name, resembling marble. Color of this rock: white, white-gray, light bluish, reddish and sometimes violet. Transparent to translucent. Anhydrite is easily hydrated, transferring into gypsum with the decrease of volume up to 30%. Anhydrite is often found in sedimentary rocks, sometimes in ore veins and low-temperature hydrothermal forms. At deposits it is usually found with gypsum. In Russia, in the Samara Region, there is the Shirmovka of anhydrite deposit. In the Krasnoyarsk Region, at Noril’sk deposits, there are layers of paurograined anhydrite of different colors: orange, rose, lilac and others; there are also concretions of anhydrite with beautiful frame of pyrite. In North Kazakhstan, at the Sokolovskiy and Sarbaiskiy mines, in magnetite ore they find lilac anhydrite. In Poland, in the area of Wieliczka, Lower Silesia, there are deposits of bluish ornamental anhydrite which has received the name darmstein. In Switzerland, at the Simplon tunnel, they discovered purple-red to violet crystals of anhydrite, up to 30 cm., available for processing, and its solid pale purple masses. In Hungary, at Recsk, anhydrite is represented with colored massive varieties of white, pale blue and pale violet hue. In Italy, near Bergamo, such solid, colored grained aggregates are called vulpinite. In Mexico, at the Naica deposit, Chihuahua State, they found bluish crystals of anhydrite up to 22 cm. Transparent crystals of colorless, bluish and violet-red anhydrite spar, sometimes, are faceted for collection purposes. So, in Canada, at a deposit with transparent crystals of anhydrite, in the region of Bancroft, Ontario Prov., they made faceted stones up to 7.75 ct. In Peru, under the general name angelite, they use concretions of light blue anhydrite, up to 12 cm., as an ornamental stone. It is processed as gypsum.

Synonyms. Bardiglionit, after the deposit in Italy | Siliceous gypsum | Karstenit | Muriacite, obs. | Bone spar | Cubic spar. | Vulpinite, after the deposit in Italy.

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