Cats-eye Quartz Enlarge
Sepr 1 1813 published by Jas Sowerby London.
Exotic Mineralogy
Silex quartzum, sericeum

Cats-eye Quartz

  • Syn.
    • Cats-eye. Kirw. 1. 301. Jameson 1. 200.
    • Œil de chat. Bournon 24.
    • Katzenauge. Emmerl. 1. 188.
    • Quartz agathe chatoyant. Haüy, Traité 2. 427, Tabl. 27.

Whether this stone be a variety of Quartz, or a distinct species, is a question not easily solved, and will probably long remain a matter of opinion among Mineralogists. In its component parts it differs so little from Quartz, that in a system regulated by chemical characters they would be arranged together. In its external characters it bears the same relation to Quartz, as Satin-spar does to Calcareous spar*, except that it is more compact. There is a variety of Feldspar with a similar lustre, that is sometimes confounded with it; indications however, of a laminated fracture will readily distinguish them. The Spec. Grav. varies, according to Klaproth, from 2.600 to 2.695.

Klaproth’s analysis gives,
Silex 95.     94.50
Alumina 1.75 2.00
Lime 1.50 1.50
Oxide of Iron 0.25 0.25

The largest specimen figured is from the Island of Ceylon, and is the same kind as the larger cut sijechnen. The other two are from the Peninsula of India. They are to be found in the Count de Bournon’s extensive collection. Rough specimens arc extremely rare in England, particularly of the variety from India.

  • * Therefore I give the same trivial name. The Satin-spar, the striated Gypsum, compact Asbestus, &c. if cut in the same form, show the same line of light that in this stone has been compared to the glare of a Cat’s eye: this comparison is here much favoured by the colour of the stone: in the mass the lustre is often obscured by the dulness of the surface, but in fresh broken specimens it is very considerable.
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