[meteorite-list] TSCHERMAK G. (1885) - Part 2

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:49 2004
Message-ID: <DIIE.0000003E00001BC2_at_paulinet.de>

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

Textures

Several different coarse textures or structures are observed in meteorites.
Many irons have no structure. They consist of a single crystal (e.g., Braunau)
or a pattern of oriented crystals (Hraschina, Toluca). Others are granular
(Zacatecas, Santa Rosa). The meteorites that are transitional between irons
and stones often have a porphyritic appearance, with the silicate grains and
crystals apparently floating in a groundmass of iron (e.g., the mass discovered
by Pallas at Krasnojarsk).

Some stony-irons contain numerous silicate grains in a delicate iron network
(Hainholz). Some irons have the character of a breccia, enclosing silicate rock
fragments (Netschaevo, Copiapo). Breccias of gray fragments cemented together
by a darker groundmass are common among the stony meteorites (Shytal, St. Mesmin,
Pulsora). Occasionally this structure is indistinct (Juvinas), and only an alter-
nation between coarse-grained and fine-grained areas can be observed.

The groundmass between fragments is occasionally black and semivitreous; it shows
traces or distinct evidence of fluid flow, as can be seen in sections of Orvinio
and Chantonnay. All gradations exist between obviously brecciated structures and
homogeneous rock; in section, the groundmasses of these may show only as fine,
dark lines running in disarray, or as areas with a cloudy texture or a marbled
appearance. Haidinger has called attention to these brecciated and tuffaceous
structures.
Received on Fri 12 Mar 2004 06:06:15 PM PST