1 88 Tlie American Geologist. March, i899 
tremolite, tourmaline, rutile, sphene, leucoxene; also an un- 
determined mineral, probably cyanite (disthene); and finally 
diamond. The olivine is often said to be fresh; the biotite 
is a prominent ingredient. Serpentine, in part bastite, calcite, 
zeolites,chalcedony, and talc occur as decomposition products. 
One occurrence of native gold in a Kimberley diamond is on 
record. This has been reported by Becker.* This diamond 
is now in the Royal Polytechnic High School at Aachen. 
Sir William Crookes, who visited South Africa early in 
1896, a few months after de Launay, treats of the origin of 
the diamond more from a physical standpoint, placing great 
stress oil the method of formation of artificial diamonds by 
M. Moissan, who used. iron as a solvent for the carbon. The 
iron, which must be thoroughly purified, is placed in a carbon 
crucible together with charcoal made from sugar, and the cru- 
cible subjected to a temperature of 4000 °C in an electric 
furnace. As is well known, iron increases in volume at the 
moment of passing from the liquid to the solid state. The 
sudden cooling solidifies the outer layer of iron and hold the 
inner molten mass in a tight grip. The expansion of the 
inner liquid on solidifying produces an enormous pressure, and 
under the stress of this pressure the dissolved rrrbon sepa- 
rates out in a transparent, dense crystal; in fact n> diamond. 
Many circumstances point to the conclusion that the dia- 
mond of the chemist and the diamond of the mine are strange- 
ly akin as to origin. It has been conclusively proven that the 
diamond has not been formed /// situ in the peridotytc-breccia. 
The diamond genesis must have taken place at great depth 
under enormous pressure. The explosion of large diamonds 
on coming to the surface shows extreme tension. There were 
probably many types of crystallization ; differing in place and 
time, or we should not see such distinct characteristics in gems 
from different mines, nor, indeed, in the diamonds from dif- 
ferent parts of the same mine. 
The finding of diamonds in meteorites is also lUilized b\- 
Crookes as further evidence of the origin of diamonds in as- 
sociation with iron. Moreover, iron is the most abundant 
impurity found in the ash of diamonds after they have been 
burned. Crookes regards the diamond as having been formed 
*George F. Becker, i6th Ann. Rep. U. S. G. S., No. 3, p. 2-72. 
