[meteorite-list] Mineral responsible for green color in Moldavite?

[bernd.pauli at paulinet.de]

Hello Chris, Elton and List,


A decreasing silica content seems to correlate with a gradual
change of color from yellow over green towards brown:

LDG - almost pure silica => 98% - yellowish or pale green
Moldavites => 78-85% - (light) bottle green
Average value of 25 bediasites => 71.89-81.31 - dark-brown to light-brown glass
Australian tektites => 66.9-68.5% / 70-73%
Muong Nong => 67-79%


Mar 23, 1998 (former?) list member *Wolfgang Czegka* posted this (excerpts):

a) Thorpe and Senftle 1964 stated that the colour of tektites is mostly given by the Fe(II)
content and that the brown colour is the result of  the presence of Fe(III) and dispersed
colloidal particles of metallic iron. 

b) In a study based on moldavites Bouska et al. 1982 pointed out that the colour is affected
both by the total iron content and by the Fe(II)/Fe(III)-ratio. The Fe(III) content is relatively
higher in brown moldavites.

c) the colour of "poisonous green" may be related to Cr2O3 (Glass 1984) or to Ni-oxides
(Bouska et al. 1982).

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Bottle-green
pre-Xmas
wishes,

Bernd