Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia



DATOLITE (Datolith—Datolite—ƒатолит) (Esmark, J. 1806), from Gk. “detéoma” – to divide, is alluding to the granular habit of some massive specimen; and “lithos” – stone.

Composition & Properties. Borosilicate – CaB[4][OH|SiO4], monoclinic system. Hardness 5-5.5. Density 2.9-3.0. Glass luster, greasy one. Cleavage in one direction. Fragile, viscous in aggregates. Datolite is represented with non-transparent grained and cryptocrystalline masses and cluster-like formations of radial-rayed structure – botryolith. The color of such aggregates can be colorless, white, reddish, orange, yellow to brown, pale green and violet. There is also datolite in the form of small columnar, isometric and lamellar crystals, usually yellow-green in color. Transparent or translucent.

Deposits. It is a typical mineral of late hydrothermal veins and metasomatism on magmatic rocks of basic composition. In Russia, in the Northern Caucasus, datolite is found in amygdales with zeolites in andesine-basalts in the Mashuk Mt., near Pyatigorsk. In the Krasnoyarsk Region datolite was found in green crystals up to 2 cm. at the Komsomol’skiy Mine, in the region of Noril’sk. In Buryatia Rep., ornamental, kidney-shaped datolite fills cavities in skarns at the Solongo deposit. In the Primorskiy Region, at the Dal’negorskoye deposit (form. Tetyukhe) they extracted ornamental hedenbergit-datolite-wollastonite skarns of spherical texture with the diameter of spheres up to 1 m. In cavities among sphaerolites in skarns, it occurs white or green datolite crystals up to 12 cm. Beside usual pale green with yellow and blue tones, these crystals can be of sea-green color. In Europe, datolite is known in South Norway, at the Arendal magnetite deposit, where cluster-shaped aggregates of botryolith were extracted as additional material. In Austria, in alpine veins of the Kratzenberg deposit, Salzburg, datolite is found in the form of transparent crystals up to 11 cm. long. In Italy, its crystals up to 8 cm. long were found at the Baveno deposit, Piedmont. In South Africa, datolite crystals available for faceting at the N’Chwaning-II deposit, Northern Cape Prov., was found. In Canada and in the U.S.A., they extracted the best gem-quality material. In Ontario they found crystals up to 3.5 cm. at the Lacey mine, Frontenac Co. In Michigan, there are common datolite crystals up to 7 cm. in cavities in native copper deposits of Keweenaw Penin. Here, porcelain-like datolite with inclusions of native copper is known. It is represented with spherical nodules up to 30 cm. in diameter, of rose, red and brown color. In Massachusetts, gem-quality datolite crystals up to 7 cm. were extracted at Lane Quarry, Hampden Co., where they made faceted stones up to 13.21 ct. In New Jersey, similar crystals up to 9 cm. at the mines Bergen Hill, Bergen Co., and in the Lane quarry, Hampden Co., are found. In Mexico, in the San Luis Potosí State, at the La Aurora deposit, in the of Charcas Dept., they found datolite crystals with danburite up to 9 cm. long.

Synonyms. Botryolith, from Gk. “botris” – a bunch of grapes and “litos” – a stone, after the shape of aggregates | Esmarkit, after Scandinavian mineralogist M. Esmark | Natrocalcite | Dystome spar | Grape stone | Sugar stone.

Treatment. In faceted form datolite is of collection interest only, because of its pale color. Faceted stones are not more than 5 ct. In jewelry bright colored varieties are used for cabochons and in stone carving.

Synthesis. Among the artificial borosilicates the most perspective for faceting is synthetic neodymium borosilicate.

Similarity. Datolite looks like apophyllite, danburite, calcite, quartz, and zeolites.