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CROCIDOLITE

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Originally appearing in Volume V07, Page 477 of the 1911 Encyclopedia Britannica.
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CROCIDOLITE , a See also:

mineral described in 1815 by M. H. See also:Klaproth under the name Blaueisenstein (See also:blue ironstone), and in 1831 by J. F. See also:Hausmann, who gave it its See also:present name on See also:account of its See also:nap-like See also:appearance (Gr. KpoKUS, nap of See also:cloth). It is a blue fibrous mineral belonging to the See also:amphibole See also:group and closely related to riebeckite; chemically it is an See also:iron See also:sodium silicate. Its resemblance to See also:asbestos has gained for it the name Cape Asbestos, the See also:chief occurrence being in Cape See also:Colony. The mineral suffers alteration by removal of See also:alkali and peroxidation of the ferrous iron, and further by deposition of See also:silica between the See also:fibres, or by their replacement by silica; a hard siliceous mineral is thus formed which when polished shows, in See also:con-sequence of its fibrous structure, a beautiful chatoyance or silky lustre. This is the ornamental See also:stone which is known when blue as " See also:hawk's-See also:eye," and when of See also:rich See also:golden See also:brown See also:colour as " See also:tiger-eye." The latter, which represents the final alteration of the crocidolite, has become very fashionable as " See also:South See also:African See also:cat's eye," and is often termed " crocidolite," though practically only a mixture of See also:quartz with brown See also:oxide of iron. The following are analyses by A. See also:Renard and C.

Klement of the unaltered crocidolite and of the blue and brown products of alteration: Crocidolite. Hawk's-eye. Tiger-eye. Silica ~— 51'89 93 45 93 05 Ferric oxide 19.22 2.41 4.94 Alumina . . . . .. 0.23 0.66 Ferrous oxide . 17.53 1.43 See also:

Magnesia . 2.43 0.22 0.26 See also:Lime 0.40 0.13 0.44 Soda 7.71 Potash 0.15 See also:Water 2.36 0.82 0.76 See also:Total . . Io1.69 98.69 Ioo•11 Another alteration product of the crocidolite, consisting of silica and ferric See also:hydrate, has been called griqualandite. Crocidolite and the minerals resulting from its alteration occur in seams, associated with See also:magnetite and other iron-ores, in the See also:jasper-slates of the Asbestos Mountains in Griqualand See also:West, Cape Colony. It is known also from a few other localities, but only in subordinate quantity.

End of Article: CROCIDOLITE

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