THE BOND SPRINGS STONY METEORITE 
51 
The nickel-iron percentage in the Bond Springs Aerolite 
is considerably higher than it is in five out of the other seven 
Australian examples. The percentage of iron sulphide 
approximates that for the other meteorites but tends to be 
lower than in most of the Australian examples. The table 
indicates the variability in the metal content of aerolites. 
The Bond Springs Aerolite is crystalline, with a micro- 
porphyritic structure, numerous chondrules of microscopic 
dimensions, and occasional small individual crystals in a 
finer-grained matrix. ]\Iost porphyritic constituents are 
under 1 mm. in diameter, the largest section observed 
measuring 150 x 0 75 mm. The majority of the chondrules 
are not much larger than the groundmass constituents, and 
many of them are unbroken. The metallic minerals rarely 
encroach upon the chondrules, and occur as scattered grains 
and lobate patches throughout the base, often partially out- 
lining chondrules and larger crystals. 
The most abundant minerals are enstatite, with (4-) 2V = 
about 60°, and olivine ; these two minerals form the chondrules, 
the greater part of the groundmass, and the occasional larger 
individual crystals. A little clinopyroxene, with extinction 
angles ranging from 6°-36° and (4-) 2V > 45°, is associated 
with enstatite in a few chondrules and to a less extent in the 
matrix; presumably it is a diopsidic augite. Micrometric 
analysis indicates that Fe-Ni metal forms 17 3 per cent, by 
weight of the meteorite and pyrrhotite 4 7 per cent. Chromite 
occurs as occasional grains. In the fine-grained, more or less 
holocrystalline matrix, which is composed essentially of 
granular enstatite and olivine, one crystal of felspar was 
observed; it has lamellar twinning, undulose extinction, and 
an extinction angle of approximately 6° in the symmetrical 
zone, and it is possibly oligoclase, but may be more basic. In 
addition, there are occasional small patches of a mineral with 
low birefringence which may be devitrified glass or possibly 
maskelynite, a glass having the composition of basic labra- 
dorite, described from certain extra-Australian aerolites. 
Isotropic glass occurs in minute quantity in the matrix of 
one of the chondrules. 
Chondrules. 
Chondrules are very abundant; the thin section, no more 
than half an inch square, contains over thirty well-defined 
chondrules of circular, ovoid and irregular shapes. In 
structure, some resemble chondrules described from the 
