As the diamond is known to be a crystal line form of common carbon, many at tempts have been made to manufacture it by artificial means. No great degree of suc cess has yet rewarded these efforts, al though very small diamonds of apparently good quality can be prepared by methods now known. Carbon being practically in fusible, it has not been found feasible to induce crystallization by causing • the carbon to solidify from a molten condition. Free car bon is soluble in but few substances, and from such solutions as can be prepared it is deposited mainly in the form of graphite. It dissolves to a considerable extent in melted platinum, but when the metal is allowed to cool and solidify, the carbon is all thrown down as graphite, and no diamonds are obtained. Of the more suc cessful experiments of this sort, those of Mois san are best known. Moissan made use of the known fact that carbon will dissolve to same eir tent in melted iron. Under ordinary conditions the carbon is here also deposited in the graphitit form; but Moissan found that when the solution is allowed to cool under an exceedingly great pressure a small portion of it appears in the form of minute crystals that possess all the properties of the true diamond, even exhibiting the peculiar pittings on the surface that are characteristic of the natural stone. His method consists in saturating the molten iron with car bon and then pouring it into a mold and chilling the casting as quickly as possible by immers ing it in water. The outer layers solidify under this treatment, while the interior is still quite fluid, and the powerful contraction of the sur face gives rise to an enormous internal pressure. As the fluid core solidifies, the greater portion of the carbon that it contains is deposited in particles that are distributed throughout the mass. The casting, when entirely cold, is dis solved in acids, and the residue is treated in various ways to effect the removal of the graph ite and amorphous carbon. A small precipi
tate remains behind, in which tiny crystals of diamond may be distinguished. No stones that are large enough to be of commercial value have yet been prepared, and while the process is of great theoretical interest, it is far too ex pensive, in comparison with the yield, to be practicable even for the manufacture of dia mond powder for polishing and grinding pur poses. Moissan's 200 experiments, costing $2,000, yielded one-half carat of diamond powder worth $1.
Minute diamonds have occasionally been found in meteorites, as in that from Carton Diablo, Arizona, at the American Museum of Natural History, New York city. This was one of the earliest instances of diamond identi fication in a meteorite, the discovery having been made by Dr. G. A. Kcenig, in 1891. The first find in a meteorite was made in 1888 by the Russian scientists Jerofeyev and Lachinov, in the case of one that fell, in 1886, three miles from the village of Novo-Ursi, in the govern ment of Perm, Russia. A piece of the meteorite from Carton Diablo was dissolved with hydrochloric acid, separating the diamond dust, some of which was used under the direc tion of the present writer to polish several ter restrial diamonds, this being the very first in stance of the polishing of an earth-born diamond by the dust of one dropped from the sky. One of these two stones is to be seen in the collection of the American Museum of Natural History.
These meteorites and diamonds were called to the attention of Dr. Henri Moissan by the present writer, and led to his further experi ments and to the discovery of moissanite (named by the present writer) — a silicide of carbon having the hardness 9.5, next to the diamond. See GEMS ; PRECIOUS STONES.