Sec. IV, Ch. 12: Semi-Precious Stones, Crocidolite

Page of 366

Text size:



	CHAPTER XII.

	CROCIDOLITE.

	ITHIN the last quarter of a century a great deal of this mineral has been brought from South Africa, and introduced into commerce as Cat's Eye ; but whilst the true Oriental Cat's Eye is a valuable and beautiful gem, this stone is comparatively worthless for jewellery. It is, in fact, mainly a ferruginous Quartz, or Chalcedony, associated with a fibrous mineral known as true Crocidolite, or a pseudomorph after it. Crocidolite is a mineral belonging to the group of Hornblendes, and consists of thin delicate silken fibres compacted together in masses, and often associated with magnetite or magnetic oxide of iron. When Crocidolite is cut en cabochon, it exhibits, in some degree, the Cat's Eye effect ; it being an optical property of all acicular or fibrous minerals, when cut with a curved surface, to show more or less chatoyancy on a line at right angles to the fibres of the substance. The colours of the Crocidolite are usually some shade of yellow, with a ray of a lighter colour ; or rich brown deepening to almost black ; or a dark indigo with a zone of lighter blue. The brown variety is known as Tiger's Eye and the blue as Hawk's Eye. The so-called Crocidolite Cat's Eye comes principally from a locality on the Orange River in Griqualand West, S

Page of 366