HOVEY, THE FOYER METEORITES 17 
taining some iron, which occurs in all the siderolites and most of the 
aérolites, sometimes comprising a considerable portion of their mass. 
It is a dark yellowish-green to black, glassy mineral usually occurring as 
rounded or angular grains, but sometimes as crystals. It is prominent 
in a slice of Brenham in the Foyer collection, where it forms glassy 
grains in a mesh of nickel-iron. Olivine is the gem, peridot. 
The minerals belonging to the group known as orthorhombic py- 
roxenes are next to olivine in point of abundance. Chemical analyses 
show that all gradations are present from the colorless enstatite to the 
almost black hypersthene members of the group. The monoclinic 
pyroxenes, which are important constituents of terrestrial igneous rocks, 
are represented in meteorites by only two forms, an iron-atumina pyrox- 
ene like common augite and one nearly free from iron and without 
alumina which is to be compared with diopside. The augite-like mineral 
is brown to green in color and occurs usually in grains or splinters rarely 
in crystals. It has been found in many meteorites, but diopside has 
been identified only once with certainty. 
The great feldspar series has been identified in meteorites in four 
of its forms, namely: anorthite, albite, oligoclase and labradorite. 
Of these, anorthite has been found forming a large part (59 per cent.) 
of some meteorites and measurable crystals have been obtained, but in 
most cases where feldspar occurs in a meteorite, it has been possible to 
go no farther than to identify it as belonging to the plagioclase section 
of the mineral group. 
Maskelynite is a transparent, colorless, glassy mineral. In chemical 
composition it is related to the terrestrial species leucite, but it is a dis- 
tinct form and thus far is known only from meteorites. It is not known 
to occur in any of the meteorites displayed in the Foyer. 
Accessory Constituents. 
Schreibersite is a phosphide of iron, nickel and cobalt which is 
probably peculiar to meteorites. It is tin-white in color, changing to 
bronze-yellow or steel gray on exposure to the air. In structure it 1s 
granular, flaky, crystalline or needle-like. Next to nickel-iron schrei- 
bersite is the most generally disseminated constituent of siderites and 
forms some of the shining lines to be seen on etched sections. 
Carbon occurs in at least three forms in meteorites, as the diamond, 
