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Criddleite, TlAg2Au3Sb10S10, a New Gold-Bearing Mineral from Hemlo, Ontario, Canada1

Published online by Cambridge University Press:  05 July 2018

Donald C. Harris ,
Andrew C. Roberts ,
J. H. Gilles Laflamme  and
Chris J. Stanley
Donald C. Harris
Affiliation:
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada K1A 0E8
Andrew C. Roberts
Affiliation:
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada K1A 0E8
J. H. Gilles Laflamme
Affiliation:
CANMET, 555 Booth Street, Ottawa, Ontario, Canada K1A 0G1
Chris J. Stanley
Affiliation:
Department of Mineralogy, British Museum (Natural History), Cromwell Road, London, England SW7 5BD
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Abstract

Criddleite, ideally TlAg2Au3Sb10S10, is a rare constituent within the Hemlo gold deposit, Hemlo, Ontario, Canada. The mineral occurs as 20 to 50 µm-sized lath-like, tabular or anhedral grains usually surrounding or penetrating aurostibite, or associated with native antimony, native gold and stibnite. Criddleite is opaque with a metallic lustre and a black streak. It has been synthesized by reacting TlSbS2 and high purity Ag, Au, Sb and S in an evacuated silica glass tube at 400 °C. The measured density of the synthetic material is 6.86; the calculated density is 6.57 g/cm3. The difference is due to minor admixed aurostibite, native antimony and a dyscrasite-like phase within the charge. VHN25 is 94–129. Mohs hardness (calc.) = 3–3 ½. In reflected plane-polarized light in air, natural criddleite is weakly bireflectant with a discernible reflectance pleochroism from grey-blue to slightly greenish grey-blue. The mineral has a distinct to moderate anisotropy with rotation tints in shades of buff to slate grey. Reflectance spectra and colour values for both natural and synthetic criddleite are given. X-ray study showed that synthetic criddleite is monoclinic (pseudotetragonal) with refined unit-cell parameters a = 20.015(2), b = 8.075(2), c = 7.831(2) Å, β = 92.01(2)°, V = 1264.9 ± 1.0 Å3 and a:b:c = 2.4786: 1:0.9698. The space group choices are A2/m(12), A2(5) or Am(8), diffraction aspect A*/*. The seven strongest lines in the X-ray powder diffraction pattern [d in Å (I) (hkl)] are: 5.63(90) (011), 3.91(50) (002), 3.456(50) (320), 2.860(70) (700), 2.813(100) (022), 2.018(60) (040) and 1.959(70) (004). Electron microprobe analyses are reported of natural criddleite in five polished sections of drill core from four holes. The averaged empirical formulae, based on 26 atoms, are Tl0.92Ag1.99Au2.93Sb9.87S10.28 (natural) and Tl0.94Ag2.03Au2.89Sb9.76S10.38 (synthetic).

Keywords

criddleitenew mineralHemlo gold depositHemloOntarioCanadareflectance dataX-ray dataelectron microprobe analysessynthesis
Type
New Minerals
Information
Mineralogical Magazine , Volume 52 , Issue 368 , December 1988 , pp. 691 - 697
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1988

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Footnotes

1

Geological Survey of Canada Contribution Number 10288.

References

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Harris, D.C. (1986a) The minerals in the main Hemlo gold deposit, Ontario. In Current Research, Part A, Geol. Survey of Canada, Paper $6-1A, 49-54.CrossRefGoogle Scholar
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