[meteorite-list] TSCHERMAK G. (1885) - Part 5
From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:49 2004
TSCHERMAK G. (1885) Die mikroskopische Beschaffenheit der Meteoriten
(Stuttgart E. Schweizerbart'sche Verlagshandlung, E. Koch, 23 pp.).
English Translation: The Microscopic Properties of Meteorites, Vol. 4,
No. 6 (Smithsonian Contributions to Astrophysics, Washington, D.C., 1964).
Translation by J.A. Wood and E.M. Wood
General Characteristics of Meteorites
Minerals and other constituents - part 1:
The different meteorite types are composed of a small
number of constituents in various com-binations.
Pure iron and nickel-iron are the main constituents of iron meteorites and
form the groundmass or iron-sponge in stony irons. Stones contain iron in
discrete particles and often in extended threads.
Graphite appears in some irons as nodular inclusions
and sometimes surrounds troilite inclusions.
Schreibersite (nickel-iron phosphide; rhabdite)
This mineral is often disseminated in iron meteorites
in irregular, angular, tabular, or needle-like inclusions.
Troilite and Pyrrhotite
Iron sulfide (FeS, named troilite by Haidinger) forms small and large
nodules and often also tabular inclusions in iron meteorites. The iron
sulfide in stones is somewhat lighter colored. Its composition and crystal
form correspond to pyrrhotite. According to Brezina, troilite also has the
crystal form of pyrrhotite. Rarer sulfur compounds are the dense, black
daubreelite, which contains chromium, iron, and sulfur; oldhamite, CaS;
Chromite appears in many meteorites in grains or octahedral crystals.
Magnetite is rare, known so far only in Shergotty, and
tridymite (asmanite) only in the Steinbach masses.
This occurs in rather large crystals and grains in several porphyry-like
irons and stony irons and in all chondrites and several other meteorite
types. Chassigny consists en-tirely of olivine.
The almost colorless or white iron-poor compound enstatite, the iron-bearing
bronzite, and the iron-rich member of the series, hypersthene, are all represented
in meteorites. Their distribution is the same as that of olivine; one meteorite type
consists entirely of bronzite.
Crystals having the form of augite, but poorer in calcium than terrestrial augite, have
been observed in several stones. Large and small grains of augite occur in many other
stones. I shall often lump together bronzite and augite as "pyroxenes."
Received on Sun 14 Mar 2004 06:36:51 AM PST