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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

VARISCITE, GROUP: VARISCITE, STRENGITE


VARISCITE group (Variszit—Variscite—¬арисцит) (Breithaupt, A. 1830), after its discovery location; Variscia is the ancient name for the Voigtland Dist., Saxony, Germany. Here also strengite is described, which forms an isomorphic row with variscite.

Composition & Properties. Variscite phosphate – Al[PO4]•2H2O. Orthorhombic system. Hardness 3.5-4.5. Density 2.2-2.5. Glass luster to wax one. It is a rare mineral, usually it forms massive fine-grained aggregates in the form of veins and nodules up to 60 cm. in cross-section, and crystals are very rare. Color: green, light bluish-green to colorless. Translucent to transparent. Well polished.

Deposits. Variscite is formed in the zone of oxidation of different types of deposits, mainly in hydrothermal low temperature veins, because of the transformation of phosphates. In Russia, variscite is described on the Chukchi Penin., at the Ichuveem deposit. In Central Kazakhstan it was discovered at the Sarysay deposit. In Tadzhikistan, at the Biryuzakan deposit, it is found together with turquoise. In Sweden, at the Kiruna deposit, Norrbotten, variscite is found in mixture with strengite. In Great Britain, in ancient Celtic tombs, they found non-transparent light bluish variscite, so called callainite. In Germany, variscite as the yellow-green variscite suns up to 3 cm. in diameter at the Mesbach deposit, near Plauen, Saxony, was discovered. There, in the region of Pegau, it is known under the name peganit. In France, in the region of Montebras, variscite occur together with wavellite. In Southern Australia, variscite is found together with turquoise at the Iron Monarch deposit, on the Eire Penin., where it is called Australian turquoise, or Australian nephrite; also and in the Queensland Prov., at the Dayboro deposit, near Brisbane – Australian jade.

As an ornamental stone, variscite was valued after the discovery of its significant accumulations in the form of nodules up to 30 cm. in the U.S.A., at Clay Canyon, near Fairfield, Utah, where it is known under the trade name utahlite, or Utah turquoise. Besides, Nevada turquoise and Californian turquoise after the discovery locations in these states, as well as in Arizona and Arkansas. A ferrous variety of variscite, is called redondite, was discovered also in the Bisbee deposit, Cochise Co., Arizona. In Utah, at the Amatrix Hill deposit, they classify three varieties of ornamental variscite in a mix with chalcedony and quartz – amatrice (amatrix). Other versions according to color have received names: Utah turquoise, apple variscite – white inside and apple-green at the edges; nephrite variscite, and netlike variscite, or green web. A banded variety of variscite with admixture natrolite is called sabalite, or trainite. In the same state, variscite is found in crystals at the Lucin deposit with trade name lucinite. In Nevada, at the Ely deposit, there is another one variety of variscite – amatrix variscite or quartz variscite, which is represented with concretions, cemented with quartz or chalcedony. They are colored concentric-zonal from green in the center to brownish at the edges. In jewelry variscite is used in the same way as turquoise. In Venezuela, redondite occur in phosphate deposits on Redonda Is., Antigua.

Synonyms. Turtledove back, after the color | Lavendulan | Utahlite matrix | Peganit, from Gk. “peganon” – grass, after the color; or after the discovery location near Pegau, Saxony, Germany | Phosphochromite | Redondite, after the discovery location on the Redonda Is., Lesser Antilles Iss. | Sphaerite (spherite), after the character of aggregates | Tangaite, after the discovery location near Tanga, Tanzania | Trainite, after the Amer. gemologist P. Train | Chlor-utahlite.

Similarity. Variscite looks like turquoise, but differs from it with the color. Turquoise becomes dark brown to black under heating, and variscite – lavender-blue. It has similarity with wavellite, verdite, jadeite, emerald, malachite, chrysocolla and chrysoprase.

Strengite (Strengit—Strengite—Ўтренгит) (Nies, A. 1877), after J.A. Streng (1830-1897), a professor of Mineralogy, University of Giessen, Germany. Phosphate – Fe3+[PO4]•4H2O, orthorhombic system. Hardness 3-4.5. Density 2.8-2.9. Wax luster. It forms an isomorphic row with variscite. It is a rare mineral, which is usually found in the form of spherolitic and kidney-shaped aggregates. Color: pale green to emerald-green, also light bluish-green to colorless, red, violet. Translucent to transparent. It looks like wavellite. It is formed in the zones of oxidation of pegmatites at iron-ore deposits. Findings of gem-quality strengite in crystals up to 2 cm. long were made in Germany, in pegmatite’s near Hagendorf, Bavaria; and at the Eleonora mine, near Giessen, Hessen. In Sweden, strengite is found at the iron-ore Kiruna deposit, Norrbotten. In Slovakia, at the Dubnik deposit its variety barrandit, named after the Czech geologist J. Barrand, was found in the form of light green sphaerolites. Other findings are known in Czech Rep., at the Príbram deposit; in Italy – in the Iglesias area, Sardinia Is.; in the U.S.A. – in pegmatites of the Pala deposit, California; in Surinam – in pegmatites of Georgeka Krik.

Solid, translucent strengite is well polished and cut in cabochon. Sometimes it is in use as turquoise.

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