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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

WOLLASTONITE


WOLLASTONITE (Wollastonit—Wollastonite—¬олластонит) (Lehman, J. 1818) after William Hyde Wollaston (1766-1828), an Engl. chemist and mineralogist; discovered palladium (1805); invented the reflecting goniometer (1809) and the camera Lucida (1812).

Composition & Properties. Silicate – Ca3[Si3O9]. subclass chain silicate, triclinic system. Hardness 4.5-5. Density 2.8-3.0. Glass luster, pearl one on the cleavage planes. Perfect cleavage in one direction. Melting temperature is 1540°C. Wollastonite is widespread mineral. Usually it is represented acicular to fibrous aggregates up to 10 cm. or more, also massive, uncommon tabular crystals. Transparent to translucent. Color: white, if calcium is replaced with manganese and iron, ferrowollastonite can be rose, red and yellow to brown. Among the rocks, containing wollastonite and of some interest as ornamental stones, we should mention hedenbergite-wollastonite and vesuvian- garnetite-wollastonite skarns.

Deposits. It is formed in significant quantities in the process of calcium metasomatism in calcareous skarns and in the rocks of the basic content. In Russia deposits of wollastonite are located in the North Urals, near Karpinsk; in East Siberia, near Minusinsk; in the Primorskiy Region, at the Dal’negorskoye deposit, where wollastonite is a rock-forming mineral for ornamental hedenbergite-wollastonite skarns. They are composed with radial-rayed and spherolitic aggregates of wollastonite with hedenbergite. The diameter of sphaerolites is rarely more than 0.5 m. Landscape varieties of these skarns are not less ornamental. Garnet-wollastonite and pyroxene-wollastonite skarns are known at many ore deposits of Middle Asia, but the evaluation of their ornamental properties was not done. In Kazakhstan, at the Ak-Dzhal deposit vesuvianite-garnet-wollastonite skarns are of special interest. In Uzbekistan, the Koytash deposit, Jizzakh Dist., of wollastonite skarns is known. In the south of Finland, ornamental wollastonite was extracted at the Lappenranta deposit and on the Pargas Is.; in the south of Sweden. In Czech Rep., such wollastonite is known at the Ζulova deposit. In Romania, aggregates wollastonite suns up to 25 cm. at the Valea Seacà deposit, near Bàita Bihor, were found; and in columnar crystals up to 20 cm. in skarns at Ciclova Montanà, near Oravita, Caraš-Severin Dept.. In Namibia, wollastonite was extracted together with petalite at the Karibib deposit. In China, wollastonite skarn at the Fengjiashan mine, here occur aggregates up to 20 cm., Hubei Prov. In Canada, crystals wollastonite 10x3x1cm. occur in rodingite bodies in serpentinites at Jeffrey mine, near Asbestos, Québec Prov. In the U.S.A., at several deposits they extract ornamental varieties of wollastonite and wollastonite rocks. In the New York State, there is the largest Willsboro deposit of wollastonite, Essex Co.; and in California crystals up to 15 cm. at the Crestmore quarry, Riverside Co. In Michigan, on the Isle Royal (Superior Lake), solid rose-red ornamental wollastonite is extract; and in Arkansas – crystals up to 20 cm. at Magnet Cove, Hot Springs Co. From them faceted stones were made up to 5 ct. In Mexico, there is the Santa Fe deposit, where a wollastonite crystal up to 3 cm. sometimes contains inclusions of rose garnet; and at the Las Chiapas mine, Sonora, pink wollastonite occur.

Synonyms. Adelforsit (aedelforsit), in place of a finding at Ädelfors, Sweden | Grammite, obs. | Okenite | Asbestos-like okenite | Board spar | Augite prismatic spar | Table-like spar | Tabular spar | Shelly stone | White stone | Vilnite, after the old name of Vilnius (form. Vilno), Lithuania | Manganwollastonite.

Treatment. Massive aggregates of wollastonite resemble jade in viscosity. Its color varieties are processed in cabochons. The most highly evaluated are cabochons with the effect of cat’s-eye. Rare transparent crystals from Canada are faceted for collection purposes. Wollastonite is also used as rough material for manufacturing of high-quality ceramic and glaze.

Similar Gemstones & Imitations. It looks like diopside, pectolite and tremolite. Sometimes massive varieties of wollastonite are colored to imitate jadeite and they can be used in stone-carving.

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