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Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia

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VIVIANITE


VIVIANITE (Vivianit—Vivianite—¬ивианит) (Cronstedt, 1758, in Werner, A.G. 1817), after J.G. Vivian, an Engl. mineralogist, who discovered the mineral at St Agnes, Cornwall, England.

Composition & Properties. Phosphate – Fe32+[PO4]2•8H2O, monoclinic system. Hardness 2. Density 2.6. Glass luster to pearl one. Cleavage in one direction. Fragile. Vivianite is found in the form of flattened, columnar and needle crystals, often forming radial aggregates and vivianite suns. In their fresh form crystals are transparent and colorless, but under the direct light they get pale blue greenish-light blue because of the process of oxidation, then their color gets darken to indigo-blue and dark greenish-blue. Transparent crystals display pleochroism from indigo-blue to intensive light blue and green-yellow. Oxidized vivianite is called kerchenite. It produces blue color in turquoise bone – odontolite.

Deposits. Vivianite is usually found in the oxidation zone of ore deposits. At sedimentary deposits it is often developing on organic remains. In Russia, vivianite was discovered in separate crystals up to 1.5 cm. in carbonatites of the Kovdor deposit, in the south-west of the Kola Penin.. In the Tamanskiy Penin., Krasnodar Region, in sedimentary layers rich with phosphates, they find vivianite crystals in hollows of fossil shells. In the Ukraine, on the Kerchenskoye deposit, in the Crimea, there is a similar deposit with radial agregates kerchenite up to 7 cm. in cross-section. In Great Britain, England, on the Cornwall Penin., at the deposits Saint Agnes and Truro, vivianite is represented with large transparent blue crystals. In Serbia, at the Trepça deposit, Kosovo, they found blue-green crystals up to 12 cm. In Romania, as blue crystals up to 10 cm. at Ilba deposit, Maramure¸ s Dept., were discovered. In Cameroon, intensive colored light blue vivianite crystals up to 1.5 m. near Anloa, N’gaoundéré region, were found in concretions from marsh ore. In Japan, at the Ashio mine, Tochigi Pref., vivianite crystals reached 15 cm. long. In the U.S.A., it is known in crystals up to 4 cm. at the Goldstrike mine, Eureka Co., Nevada; in Idaho, gem-quality vivianite crystals up to 12 cm. were extracted in the Blackbird Dist., Lehmi Co.; in Virginia as crystals up to 12 cm. at Richmond, Henrico Co. In Bolivia, in ore veins as superb transparent dark green vivianite crystals up to 25 cm. at the Monserrate mine, near Poopó; at the Morococala mine, in especially good crystals at Huanuni, all Oruro Dept. were extracted. In 1997, at the Tucson gemstone show, the U.S.A, druses of vivianite from Bolivia were evaluated up to $2,400 per a sample. In Mexico, well-formed crystals of vivianite up to 8 cm. at the San Antonio mine, Chihuahua State, are extracted for collection purposes.

Synonyms. Angelardite | Glaucosiderite | Blue iron | Kerchenite, after the discovery location on the Kerch Penin., Ukraine | Prismatic iron mica | Mullicite, after the discovery location at the Mullica Hill deposit, Connecticut, the U.S.A. | Blue iron ore | Blue iron spar.

Treatment. From gem-quality vivianite crystals they make faceted gems for collection purposes. Under low heating they become sky-blue, that’s why vivianite was used for the imitation of turquoise. At the market the most popular are shells filled with crystals of vivianite.

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