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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

COAL


FOSSIL COALS (Fossile Kohlen—Fossiles charbons—»скопаемые угли) Fossili coals are the product of the coalification of plants’ remnants in rock layers. Among them, there are, the following varieties, which are used as ornamental stones or found as inclusions in gemstones: anthracite, cannel coal and lignite.

Anthracite (F. Senft, 1857) from Gk. “antrax” – coal. Highly metamorphic variety of fossil coal with bright half-metallic luster, sometimes with iridescent blueing. The content of C – 85-95%. Hardness 2-2.5. Density 1.3-1.7. Glass luster to metallic one. Amorphous. In the Victorian age, in America, carving on coal was popular. For instance, Pennsylvanian anthracite was used for the manufacturing of cameos, cabochons and non-expensive bijoux. Vietnamese masters skillfully carve figures of animals from anthracite. In Germany, anthracite is called brilliant coal or coal hornblende, and in Great Britain – hard coal.

Cannel coal, or cannel (Sinclair, J. 1793) from Br. “candle”, because they made candles from the wax, extracted from these coals. It is a solid variety of sapropelic coal composed with fine grinded fragments of vegetative material. On the sharp bends its surface plays silver luster. Cannel coal is worse than jet for polishing. In Russia, cannel is extracted at the Cheremkhovskiy coal-basin of the Irkutsk Region, at the Mataganskoye and Khakhareiskoye deposits of the same region and in the Tulunskiy Dist., at the Zorinskoye and Burtinskoye deposits. Under the trade name Siberian jet it is used for imitation of jet. In 1894, it was used in the decoration of the interior of the main Cathedral in Irkutsk. In Scotland, big pieces of Cannel coal were used not only for adornments, but also for furniture coating. In the British Museum, London, there is a collection of carved figures from this coal and a brooch-cameo, 10x12.5 cm. in size.

Lignite coal, or lignite (Campbell, M.R. 1908), from Lat. “lignum” – timber, fossil. It is a merely coalification timber of brown color with preserved wooden structure. The content of carbon – 65-75%, density 1.1-1.3. It is also called brown coal. In Great Britain and Germany, it was found during excavations of Ancient Roman settlements as imitations of jet in different products.

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