[meteorite-list] Classification of Meteorites (Part 2a)

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Mon Jul 4 13:30:03 2005
Message-ID: <DIIE.0000002100003A1F_at_paulinet.de>

AL kindly wrote:

> [Tschermak] again refined the system in 1883.

Here is a breakdown of Tschermak's 1883 classification system:

I. Calcium-rich stones, poor in metallic iron.
II. Magnesium-rich stones, poor in metallic iron.
III. Magnesium-rich chondritic stones with metallic iron.
IV. Iron with silicates.
V. Iron meteorites.

Within this outline, meteorites are further broken down according to their
petrography, each class having a particular mineralogical composition or
a characteristic structure.

To the classes recognized by Rose, I have added several more which I had
proposed earlier (Tschermak, 1872a). My latest studies have determined
more accurately the compositions of several of the classes, and meteorites
of new composition have been found, so that in several cases it was necessary
to transpose names and propose new names of classes.

The meteorite types known to date are:

I. Main constituents are pyroxenes and plagioclase. The crust is glossy.

- Eucrites (Rose). Augite and anorthite (or maskelynite).
- Howardites (Rose). Augite, bronzite, anorthite.

II. Pyroxenes and olivine form the main constituents.
    The crust is slightly glossy to dull.

- Bustites* (Tschermak). Diopside and enstatite. (*bustites = now aubrites)
- Chladnites+ (Rose). Enstatite with a little anorthite.

+Only Bishopville at Tschermak's time but Bishopville is an aubrite (!)

- Diogenites (Tschermak). Bronzite.
- Amphoterites (Tschermak). Bronzite and olivine. (now LL chondrites)
- Chassignites (Rose). Olivine. (now SNC)

III. Bronzite, olivine, iron as main constituents.

Chondrites (Rose). Texture chondritic.

IV. Iron, forming networks, enclosing silicates:
    plagioclase, olivine, pyroxenes, troilite.

- Grahamites (Tschermak). Plagioclase, bronzite, and augite,
    in iron. (Vaca Muerta was a grahamite for Tschermak)
- Siderophyres (Tschermak). Bronzite in iron. (Steinbach)
- Mesosiderites (Rose). Bronzite and olivine in iron.
(Lodran (!) and Hainholz were mesosiderites for Tschermak)
- Pallasites (Rose) - Olivine in iron.

V. Iron with subordinate troilite, schreibersite, etc.

Iron meteorites.

I have omitted the name shalkite, proposed by Rose for the mixture of
bronzite and olivine, because reports on the composition of Shalka are
contradictory. Instead of this I wish to propose the name amphoterite;
and for pure bronzite stones, the name diogenite. The new meteorite
type under IV also needed a name, for which I chose grahamite; and
finally the masses from Steinbach were considered a special type
(siderophyre).


Reference:

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
Received on Mon 04 Jul 2005 01:06:46 PM PDT