[meteorite-list] Tschermak and Eucrites - Part 1 of 3

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:55 2004
Message-ID: <DIIE.0000003800001D1F_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

Description of Meteorite Types

The calcium-rich stones, poor in metallic iron: Eucrites

Juvinas, Stannern, Jonsac

Juvinas, Jonzac, Stannern, Petersburg, and Constantinople belong to this class.
They consist essentially of augite and anorthite. Juvinas will be described in detail.
As Rose has noted, the texture varies considerably from place to place in Juvinas,
ranging from fabrics of small-grained crystals to indistinct fine-grained areas which
under the microscope appear crystalline to tuffaceous. Thus, the whole has a poorly
defined brecciated character. The anorthite crystals are euhedral. Where they occur
in small druses ... a tabular form. The crystals are in part clear as water, in part
white and cloudy with inclusions. Extreme magnification reveals rounded glass inclusions
and fine needle-shaped objects, oriented parallel to the crystal surfaces. Optical prop-
erties are in general the same as in anorthite from Vesuvius.
The anorthite is usually twinned, sometimes appearing in complicated systems of twins.
Crystals are about 2 mm long. In thin-section the anorthite appears bluish by incident
light, brownish by transmitted light. It is uncommonly rich in very small inclusions; most
of these are colorless, a few are brown. Most inclusions are rounded, but many are elongated;
all are bounded by extremely fine (thin) outlines. Occasionally they contain a bubble; a few
include small black grains. The inclusions are not birefringent. They are usually elongated
parallel to ..., and lie in rows parallel to the long dimension of the host crystal. The rounded as
well as the elongated inclusions are apparently glass. Inclusions with heavier outlines, which
are gas-filled cavities, are rare. Augite crystals that occur in druses are brown-black. Their
habit is that often exhibited by diopside.
Received on Sat 27 Mar 2004 01:16:35 PM PST