f W. Luzi, who found that it can be corroded by the
solvent action of fused blue ground; from the experiments of J.
Friedlander, who obtained diamond by dissolving graphite in fused
olivine; and still more from the experiments of R. von Hasslinger and
J. Wolff, who have obtained it by dissolving graphite in a fused
mixture of silicates having approximately the composition of the blue
ground. E. Cohen, who regarded the pipes as of the nature of a mud
volcano, and the blue ground as a kimberlite breccia altered by
hydrothermal action, thought that the diamond and accompanying
minerals had been brought up from deep-seated crystalline schists.
Other authors have sought the origin of the diamond in the action of
the hydrated magnesian silicates on hydrocarbons derived from
bituminous schists, or in the decomposition of metallic carbides.

Of great scientific interest in this connexion is the discovery of
small diamonds in certain meteorites, both stones and irons; for
example, in the stone which fell at Novo-Urei in Penza, Russia, in
1886, in a stone found at Carcote in Chile, and in the iron found at
Canon Diablo in Arizona. Graphitic carbon in cubic form (cliftonite)
has also been found in certain meteoric "irons," for example in those
from Magura in Szepes county, Hungary, and Youndegin near York in
Western Australia. The latter is now generally believed to be altered
diamond. The fact that H. Moissan has produced the diamond
artificially, by allowing dissolved carbon to crystallize out at a
high temperature and pressure from molten iron, coupled with the
occurrence in meteoric iron, has led Sir William Crookes and others to
conclude that the mineral may have been derived from deep-seated iron
containing carbon in solution (see the article GEM, ARTIFICIAL). Adolf
Knop suggested that this may have first yielded hydrocarbons by
contact with water, and that from these the crystalline diamond has
been formed. The meteoric occurrence has even suggested the fanciful
notion that all diamonds were originally derived from meteorites. The
meteoric iron of Arizona, some of which contains diamond, is actually
found in and about a huge crater which is supposed by some to have
been formed by an immense meteorite penetrating the earth's crust.

It is, at any rate, established that carbon can crystallize as diamond
from solution in iron, and other metals; and it seems