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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

APOPHYLLITE


APOPHYLLITE (Apophyllit—Apophyllite—јпофиллит) (Haüy R.J., 1806). From Gk. “apo” – away and “phyllazein” – to get leaves, alluding to its exfoliation when heated with a blowpipe. Before C. Rinman has found it in Sweden, on Gotland Is., in 1783 it was also named Hellestade’s zeolite or impressed zeolite. Then, d’Andrada J.B. has named it ichtiophtalm or fish-eye, because of nacreous play of light on basal planes.

Composition & Properties. On composition subdivided natroapophyllite – NaCa4[F|(Si4O10)2]•8H2O, and also fluorapophyllite and hydroxyapophyllite. Accordingly this lamellar silicate may be orthorhombic or tetragonal system. Hardness 4.5-5. Density 2.3-2.5. Glass luster, nacre one along the cleavage plane. Perfect cleavage in one direction. Fragile. Apophyllite is found in the shape of short-columnar, pseudocubic and table crystals and complete masses. Color: colorless, white or pink, dark red, yellowish, greenish or bluish. The distribution of color is obviously zonal or sectorial sometimes, with its strengthening at the edges of crystals. The color is connected with admixtures: pink – manganese (Mn3+) or cobalt, green – VO2+ or manganese (Mn4+), yellow – neodymium (Nd3+). A variety with nacre tint is called fish eye and green apophyllite is called xylochlor.

Deposits. Apophyllite is formed in basalt amygdales, in cavities in granites, in veins of natrolite among syenites, in skarns and metamorphic rocks. In Russia, in basalts of West Siberia, at deposits of Icelandic spar in the basin of the Lower Tunguska River, pink apophyllite in crystals up to 10 cm. long is widespread. They also described inclusions apophyllite in crystals Icelandic spar and quartz pseudomorphs on apophyllite there. In the Noril’sk group of deposits, especially at the Talnakh deposit, they found transparent crystals of apophyllite up to 11.5 cm. in cross-section. In Yakutia, during the retrograde transformation of charoite in the Murun massif a specific variety of it is formed with the content of apophyllite. In the Primorskiy Region, at the Dal’negorskoye deposit, they found pink apophyllite. In Azerbaijan, at the Gadabay (Kedabek) locality apophyllite is pink because of the admixture of cobalt. In Georgia, in the Pers village, a bright pink apophyllite fills cavity of amygdales in effuses with the cross-section up to 20 cm., and in the Akhalts’ikhe region they find light bluish-green vanadium-containing apophyllite as well as quartz pseudomorphs on it. In other countries, apophyllite is known in cavities of ball basalts on the Faeroes Iss., Denmark. In Germany, at the Andreasberg deposit, near St Andreasberg, Lower Saxony, they found its pink columnar crystals. In Czech Rep., in the region of the Mariánská Hora, near Ústí nad Labem, there were findings of crystals of apophyllite up to 2 cm. In Hungary, at the Recsk copper mine, they discovered colorless table crystals of apophyllite up to 5.5 cm. In South Africa, at the N’Chwaning mine and at other manganese deposits of the desert of Kalahari, they find pink table crystals of apophyllite, available for faceting. In India, in the Mahäräshtra State, at the deposits: Jslgoan, Aurangabad Dist., Pashan, near Poona, and at the Pandulena Hill, near Nashik, there are transparent colorless, light bluish-green and apple-green apophyllite crystals up to 15 cm. in cross-section. Druses aggregates of apophyllite from those places are highly valued as collection material. Such a piece of ore, 30x30 cm. in size, was evaluated in $5,500 at the gemstone show in Tucson, the U.S.A., in 1997. In China, in the Liaoning Prov., there is a deposit, from which large lamellar crystals of apophyllite came to the market. In Canada, in Québec, at the Jeffrey mine, near Asbestos, they found crystals of apophyllite up to 4 cm. in cross-section. In the U.S.A., at a Bergen Hill deposit in New Jersey, Passaic Co., the size of apophyllite crystals reached 20 cm. In Virginia, at the Centreville deposit, Fairfax Co., they found its large colorless crystals; and also in Pennsylvania – at the French Creek mine. In Brazil, at the Bento Gonçalves deposit and others, in the Rio Grandi do Sol State, they discovered apophyllite crystals up to 20 cm. In Mexico, in the region of La Luz, Guanajuato State, there is a deposit, which is the main supplier of pink crystals of apophyllite to the market.

Synonyms. Albin, from Lat. “albus” – white | Brünnichite | Fischaugenstein, Germ. | Apophyllite fishe-eye | Mosaic fish-eye | Stone fish-eye | Tesselite, from Lat. “tessela” – mosaic stone | Xylochlor, from Gk. “xylon” – wood and “chloros” – green, after its color.

Treatment. Because apophyllite is difficult in processing, it is almost never used in jewelry, staying the object for collectors. The best gem-quality materials for faceting are colorless crystals from India, from which it is possible to make stones up to 15 ct. Stones with pearls luster are cut in cabochons. In the Smiths. Inst., Wash., there is a colorless apophyllite of a step pattern of faceting, 15.4 ct.

 

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