[meteorite-list] TSCHERMAK G. (1885) - Part 6
From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:50 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 2:
Crystals and grains of anorthite are a principal constituent of several stones.
Many stones contain grains of plagioclase which may very well not have the
composition of anorthite.
This has the composition of plagioclase but is optically isotropic.
Glass is often present in meteorites, in addition to the crystalline constituents.
Some glasses are colorless, like maskelynite; others are colored, usually brown,
and often show incipient devitrification, usually into magnesium silicates.
Carbon and hydrocarbons soluble in alcohol
These have been found in black meteorites, along with a carbonate having the
properties of breunnerite. Many writers hold that the water in these stones is
secondary in origin, since most meteorites contain no water; and that sulfates
are of secondary origin, formed by the weathering of iron sulfide.
Finally, some reports speak of meteoritic constituents which have not been
confirmed, such as lead, pyrite, leucite, or sulfur, or which were given
new names but later shown to be familiar minerals, such as shepardite and
G. Rose (1864) has proposed a classification of the meteorites according to
their principal minerals, which begins with the irons and ends with those stones
most similar to terrestrial rock types. This sequence is approximately in order
of decreasing specific gravity and forms a geologic column to the extent that the
parallel drawn by Daubree (1870) is correct; namely, the metallic core of the earth
is the oldest structure, and the less dense silicate masses are younger. If the
meteorites are fragments of one or several small planets, we would expect these
planets to have a structure similar to that of the earth: a metal sphere surrounded
by an igneous, tuffaceous, silicate shell (Tschermak, 1875). Thus the Rose classi-
fication is consistent with the current conception of planetary formation, and,
for that reason, could be called the natural classification.
Received on Mon 15 Mar 2004 06:50:49 AM PST