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NUMBER 19 109
FIGURE 5.—Coarse silicate texture, inclusion 8: a, transmitted light (black areas are graphite),
note graphite "nibbling" at silicate grains; b, reflected light, crossed polarizers.
quently of the silicates is rather constant. It is
interesting that the amount of silicates in these
three inclusions of 75.9%, 77.3%, and 74.5% is
quite close to the average silicate portion of Hchondrites,
which is 76% (Table 7). The silicate
portion of two of the three inclusions analyzed
chemically is higher, but this does not give the true
silicate amount, as coarse metal particles were
removed prior to analysis.
In addition to the main minerals listed in Tables
1 and 2, the following accessory minerals were
found: schreibersite and cohenite (at the border to
the metal host), apatite, chromite, and sphalerite.
The apatite is a chlorapatite; the microprobe
analysis of 11 grains in different sections gave an
average (in weight percent) of CaO, 52.6; P2O5;
41.1; Cl, 6.00; FeO, 0.30; MgO, 0.11; Na2O, 0.46;
F is not determined, sum 99.2 (corrected for
Cl = 0). This is smiliar to the composition of the
Campo del Cielo apatite published by Bunch, Keil,
and Olsen (1970). The silicates often contain small
inclusions, mostly troilite or metal. Veining with
iron oxides formed by terrestrial weathering is
found in most specimens.
Mineral Composition
In Table 2 the orthopyroxene, olivine, diopside,
plagioclase, and K-feldspar compositions are given
for one inclusion as determined by standard procedures
with an ARL SEMQ microprobe. The
results were corrected by the method of Bence and
Albee (1968). During the study of these inclusions
it was found that small differences in the Fe/