Tracy Latimer wrote:
> Chemical composition of the stone is NaCrSi2O6 (Ureyite) ...
> The ureyite is what is supposed to be in meteorites, as a very
> dark green, almost black, mineral.
Hello Tracy and List,
That's right, ureyite (Harold Clayton Urey, 1893-1981) is an
inosilicate and it does occur in meteorites - a very important
representative is no less a celebrity than Orgueil:
GRESHAKE A. and BISCHOFF A. (1996) Chromium-bearing phases
in Orgueil (CI): Discovery of magnesiochromite (MgCr2O4), ureyite
(NaCrSi2O6), and chromium-oxide (Cr2O3).
[Abs. Lun. Planet. Sci. 27, 461-462].
see also:
BUCHWALD V.F. (1975) Handbook of Iron Meteorites, Vol. 2, p. 392:
The troilite is either pure or it contains varying proportions of
graphite, daubreelite, chromite, sphalerite, ureyite and silicates.
FRONDEL C. and KLEIN C., Jr. (1965) Ureyite, NaCrSi2O6
- A new meteoritic pyroxene (Science 149, pp. 742-743):
Description of a new mineral, ureyite, a chrome pyroxene
from Coahuila (IIAB) and from Hex River (IIAB).
The authors found polycrystalline, emerald-g r e e n aggregates,
0.1-0.5 mm in size, associated with daubreelite in Hex River; this
is probably the g r e e n mineral previously reported by Cohen.
BUCHWALD V.F. (1975) Handbook of Iron Meteorites, Vol. 3, p. 1149:
In one place a green, pyroxenoid mineral, 0.5 x 0.2 mm in size, is
embedded in troilite. It is emerald-green under crossed Nicols and
is perhaps ureyite (= kosmochlor), described by Frondel and Klein
(1965) from Toluca and Coahuila.
BUCHWALD V.F. (1975) Handbook of Iron Meteorites, Vol. 3, p. 1210:
Frondel and Klein (1965) described ureyite, NaCrSi2O6,
a new meteoritic pyroxene; evidently another confirmation
of an observation by Laspeyres (1897), who had called the
emerald-green mineral k o s m o c h l o r.
LASPEYRES H. (1897) *Die steinigen Gemengtheile im Meteoreisen
von Toluca in Mexico (Zeitschrift f�r Krystallographie 27, pp. 586-600).
*Translation: The stony components in the meteoric iron
from Toluca, Mexico (Journal of Crystallography)
Cheers,
Bernd
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