Zoisite Enlarge
[Undated]
Exotic Mineralogy
CXXIII
Silex Zoisii

Zoisite

  • Syn.
    • Zoïsite. Werner and Karsten. Haüy Journal des Mines, No. 113, p. 465. Tabl. 44. Bournon Catal. 67 & 68. Aikin 223.

Zoïsite, so named in honour of Baron Von Zois, having been descrihed as a new mineral by Werner and Karsten, has, by several authors, at the head of whom is Haüy, been referred to Epidote: still, however, mineralogists seem unsettled; and while some consider the difference of lustre and colour as important characters, others, laying aside these, seek for a radical distinction in the form of the nucleus: thus Bournon doubts whether the terminal plane of the prism be perpendicular to the sides. Bournon also notices what he considers a characteristic difference in the proportions of Silex and Iron contained in it. Without venturing an opinion until further researches shall make us better acquainted with the substance, I give a figure from an authentic specimen sent me by Prof. Strömeyer: it was obtained from Fichtelberg, in Bareuth: the crystals shoot through a large grained white Granite, in which the Feldspar predominates: the Feldspar is often interposed between the laminæ of the Zoïsite.

I add, also, a representation of a substance from Scotland, I think from Glen Elg, nearly resembling the Zoisite, but less regularly foliated, and of a more waxy lustre, characters by which it approaches to Diallage: it is in a matrix of white compact Feldspar.

Analysis of Zoisite from the Alps, by Klaproth:
Silex 45
Alumine 29
Lime 21
Oxide of Iron 3
Loss 2
100
Analysis of Zoisite from the Valais, by Lauguier:
Silex 37   
Alumine 26.6
Lime 20   
Oxide of Iron 13   
Oxide of Manganese 0.6
Water 1.8
Loss 1   
100
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