Diatnonds in California. — Turner. 187 
Finally, water accompanied the eruption of the peridotytc 
and caused its serpentinization. De Launay in his descrip- 
tion of the formation of diamonds in depth evidently has in 
mind the method of Moissan of forming artificial diamonds, 
to which, indeed, he refers. This method will be noted fur- 
ther on. While most of the diamonds show their proper 
crystalline form, there are many broken crystals, but no two 
fragments found near together ever belong to the same crystal, 
which clearly indicates transportation, as broken crystals never 
form in nature. Such broken crystals may be compared to 
the broken and corroded phenocrysts of igneous rocks, which 
are regarded as of intratelluric origin. Indeed, according to 
de Launay, the other original phenocrysts of the peridotyte- 
breccia, the olivine, garnet, enstatite, etc., likewise give evi- 
dence, in their corroded and broken forms, of having crystal- 
lized in depth. 
Lewis does not appear to have visited South Africa him- 
self, and his book is largely taken up with a description of the 
diamond rock and the fragments of other rocks included in 
it. Some of his conclusions, therefore, have not the value 
of those of de Launay or of Crookes. According to Lewis 
the diamonds are crystallized in sharp octahedrons and do- 
decahedrons. Carbonados and black diamonds are not only 
found in large crystals but are very common as minute and 
almost microscopic crystals. The abundance of these crys- 
tals is another proof that they are not inclosures brought \\\) 
from some other matrix. Lewis states that only the peridotyte 
that is full of fragments of shale and other impurities contains 
the diamonds. * These shales are highly carbonaceous so 
that they burn readily. The fragments of shale enclosed in 
the peridotyte are more compact and have lost their shah- 
character, their bituminous or carbonaceous matter, and their 
sulphur. The microscope shows also that they have frequent- 
ly been mineralogically altered by the heat of the lava' and 
become filled with aggregates of micaceous minerals. 
Lewis gives the following minerals as occurring in the 
peridotyte (kimberlyte) : olivine, enstatite, chrome-diopside. 
smaragdite. biotite, garnet, perovskite, magnetite, chromite, 
ilmenite, picotite; and more rarely apatite, epidote, orthite. 
♦Judging from the description of de Launay, this is an error. 
