MINERAL CONSTITUENTS OF METEORITES. 
361 
The blackened aspect of some of the bronzite was due to a mere superficial coating 
of iron oxide, arising doubtless from the oxidation of a portion of the nickeliferous iron. 
It was invariably found that this film was easily removed by hydrogen chloride, leaving 
the bronzite of a bright green colour, and that the action of the acid on the mineral 
extended no further. 
Two analyses of this mineral were made, the one by the hydrogen fluoride method of 
distillation*, the other by fusion with mixed alkaline carbonates, and the results were as 
follow 
I. 
II. 
Mean. 
Oxygen. 
Silicic acid 
. 56-101 
56-002 
56-051 
29-89 
Magnesium oxide . 
. 30-215 
31-479 
30-847 
12-34 
Iron protoxide . . 
. 13-583 
13-295 
13-439 
2-97 
99*899 
100-776 
100-337 
These numbers correspond very closely with the formula (Mg* Fey) Si0 3 . 
XIV. Silica crystallized in the Rhombic System , as a Constituent of the Breitenbach 
Siderolite. 
It has already been stated that the second mineral associated with the bronzite in 
this meteorite is free silica, possessing the lighter specific gravity presented by quartz 
after fusion, and crystallized in forms that belong to the orthorhombic system. To 
this mineral, which is distinct in its system and forms from the tridymite of Vom Rath, 
I propose to give the name Asmanite A'sman, being the Sanscrit term (corresponding 
to the Greek uk/uw) for the thunderbolt of Indra. In bulk it forms about one-third of 
the mass of mixed siliceous minerals. The grains of this mineral are found mixed with 
those of the bronzite after the iron, the troilite, and the chromite have been removed. 
They are very minute and much rounded, and, though entirely crystalline, they very rarely 
indeed present faces that offer any chance for a result with the goniometer ; indeed out of 
the several thousand of these little grains comprised in some two grammes that were iso- 
lated of the mineral, it was only possible to find with a lens about a dozen specimens 
with sufficiently distinct crystallographic features ; and of these only four or five proved 
to be available for examination and comparison. In several, however, the optic axes were 
plainly to be distinguished when properly examined with a Norrenberg’s polarizing 
microscope ; and by this means the angles given by planes belonging to zones otherwise 
too incomplete for a reliable result were brought into comparison on different crystals. 
Fortunately one minute crystal was met with in which the consecutive planes in half 
of the zone [1 0 0, 0 01] were complete enough to give reliable data for two of the 
parametral ratios, while the planes of the form (1 1 0) in the zone [0 01, 010] were all 
present, and one of them sufficiently brilliant to give an image by reflection. 
This crystal, designated by the letter C in the subjoined Table (p. 363), enabled me 
to make use with confidence of the approximate measurements obtained on the other 
crystals, and the more so as in the polariscope it was easy to recognize in the normal to 
the plane 10 0 the first mean line of the optic axes. 
* Philosophical Transactions, 1870, p. 189. 
3 d 2 
