[meteorite-list] Tschermak and Eucrites - Part 3 of 3
From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:55 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
Description of Meteorite Types
The calcium-rich stones, poor in metallic iron - Eucrites:
Juvinas, Stannern, Jonzac
Although they are not easily explained, the properties described above give
the impression that the originally tuffaceous groundmass was remelted and
that anorthite and purified (inclusion-free) diopside crystallized out of the melt.
The yellow plates would then be paramorphs. The remelting of a porous ground-
mass would explain the existence of the many small druses. Opaque constituents
are rare in Juvinas; pyrrhotite, chromite, and nickel-iron have been recognized.
Rose has found pyrrhotite crystallized in druses and has determined its form. He has
also observed nickel-iron, which is very rare. Besides these, I found iron-black grains
which have the properties of chromite.
The eucrite Stannern is quite similar to Juvinas, but its structure is more pronouncedly
tuffaceous (Rose, 1864, and Tschermak, 1872c). In the same specimen, granular,
radiating fibrous, and almost cryptocrystalline fragments and debris can be seen mixed
together. Some individual stones of the Stannern fall are granular like Juvinas; others are
much darker in color and fine-grained to cryptocrystalline in texture.
The anorthite and augite have the same properties in Stannern as in Juvinas, except that
well-developed crystal faces are less common; instead, the two minerals often form an
intergrowth of alternating plates. The yellow silicate and troilite are also present in Stannern.
The Jonzac meteorites are very similar to Juvinas. According to Rose, the Petersburg
(Tennessee) meteorite resembles Stannern in its petrography.
Received on Sun 28 Mar 2004 03:26:39 PM PST