ORIGIN OF THE DIAMOND          389 crystallization, of the matrix in which it occurs, appears evident from the fact that diamonds have been found in eclogite, itacolumite and an igneous rock. Profes­sor Bonney found ten small diamonds embedded in a bowlder of eclogite from one of the Newlands pipes in Griqualand West. It is reported also that they are found occasionally in the Roberts-Victor mine in the same matrix. In Brazil though usually found in drift, they occur to a limited extent in the itacolumite, thought to be the original matrix, and which by decomposition furnished the diamondiferous quartz pebble drift. Some geologists think that the Semri sandstone of India was the matrix there, because many fragments of it are found with the diamonds in the quartzose conglomer­ate which is the diamondiferous material of some parts of India. A diamond was found embedded in horn­blende diabase at Oakey creek near Inverell, Australia. The sparse occurrence of diamond crystals in unal­tered igneous rock, and their abundance in the kimber-lite breccia, suggests that crystallization occurred during the metamorphosis by hydration of an igneous magma composed of favorable reducing chemical constituents. That the crystallization of carbon can, occur under in­tense heat and pressure has been demonstrated by Pro­fessor Moissan, but that the heat and pressure was applied in the same manner in the diamond chimneys appears doubtful, for in them, the quantity of diamonds de­creases with the approach of the diamondiferous material to the source of heat, and the associate minerals are chiefly silica and magnesia. A natural solvent for carbon with sufficient heat to cause the necessary chem­ical reactions, and pressure, is probably Nature's method of crystallizing carbon.