Oxide of Chrome Enlarge
Oct 1. 1812 published by Jas Sowerby London.
Exotic Mineralogy
LIX
Cerium oxygenizatum

Oxide of Chrome

  • Syn. Chrome oxidé. Bournon Catalogue, 459.

Discovered in the mountains called Écouchets, near a village of the same name, on the road from Creuzot to Couches, in the department of the Saone and Loire, by M. Leschevins, about the year 1809 or 1810.

The upper figure is taken from a specimen of the variety which is found in layers, from half a line to three lines in thickness, in a fine-grained grey grit, composed of grey Quartz with a little Mica. The Oxide of Chrome is never found but in combination with Silex. Its colour, after being exposed to the air, is a pale opaque verdigrease green.*

According to Leschevins it is easy to scratch with a knife, when it is newly taken out of the rock, but it acquires hardness by exposure. It is rough to the touch; its fracture is unequal, earthy; its powder is of a pale dull green. It is insoluble in Nitric Acid; it communicates to glass of Borax a superb emerald green. Being analyzed by M. Drapiez of Lisle, it is found to conlain

Silex 64.0
Alumine 23.0
Oxide of Chrome 10.5
Lime and Magnesia 2.5
Iron and Manganese, a trace
100

Vauquelin found but seven per cent, of Oxide of Chrome, but it appears to vary much in quantify, and that the specimen analyzed by Drapiez was from a diflerent layer. Spec. Grav. 2.5714.

The lower specimen is a mass of rather opaque reddish Quartz, traversed by veins of a silicious substance, coloured by Oxide of Chrome in a small proportion. The middle of the veins, where they are broadest, have a reddish tinge, and the green is much more intense at the edges. The whole veins have the waxy appearance of Hornstone. It is from the same place as the upper figure; both were lent me by the Count de Bournon.

  • * Leschevins says it is of a fine apple green, a term which I very much object to, as it conveys no definite idea, and I certainly never saw an apple at all resembling this substance in colour.
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