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Non-equilibrium highly anisometric crystals and whiskers of galena

Published online by Cambridge University Press:  05 July 2018

I. K. Bonev
I. K. Bonev*
Affiliation:
Geological Institue, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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Abstract

Unusual irregular galena crystals and whiskers were found in close proximity in some druse cavities from the Gradishtc hydrothcrmal lead-zinc deposit in the Madan ore district, Bulgaria. The following crystal forms were observed: (1) straight thin [110] whiskers and thicker needles; (2) kinked whiskers; (3) curvilinear whiskers; (4) complex tortuous whiskers composed of segments with varying directions—[110], [100], [211], (5) thicker irregular elongated crystals. Combinations of these forms occur also. The detailed SEM study shows that all these formations are single crystals of extreme anisometricity, bounded by octahedral and cubic faces as well as by stepped surfaces of these forms. Surface structures such as longitudinal grooves, jagged edges, striations, pits, etc., are abundant.

It is assumed that these highly non-equilibrium crystals with large surface areas were formed through rapid directed growth from highly supersaturated solutions under a diffusional regime. Such special environments arose in the ore veins as a result of tectonic shocks leading locally to a drastic volume increase and P and T decrease in the solutions.

Keywords

galenacrystal morphologycrystal growthwhiskersMadan ore district
Type
Mineralogy
Information
Mineralogical Magazine , Volume 57 , Issue 387 , June 1993 , pp. 231 - 240
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1993

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