SPECULATIONS REGARDING THE GENESIS OF THE 
DIAMOND. II 
ORVILLE A. DERBY 
Geological and Mineralogical Service of Brazil, Rio de Janeiro 
Since writing the paper with the above title that appeared in 
the October-November, to11, number of this journal Fersmann 
and Goldsmidt’s monographt on the crystalline form of the diamond 
has come to hand and its perusal has suggested some additional 
observations on the subject. 3 
From the genetic point of view the most important deduction 
drawn by the authors from their epoch-making studies is stated on 
p. vu of the Introduction in the following terms: All the diamond 
crystals known to us have been formed suspended in a molten mother- 
liquid (magma). Since the present paper is of a speculative nature, 
I venture to restate, provisionally, this law as follows: Diamond 
crystals have been formed suspended in a medium sufficiently mobile, 
or susceptible to solution (replacement), to permit their free, all-round 
development. The most essential difference between the two forms 
of statement is the elimination in the latter of preconceived ideas 
regarding the physical condition of the enclosing rock at the moment 
of the crystallization of the mineral. 
Another important deduction from the studies of Fersmann and 
Goldsmidt is the extreme delicacy of the saturation point for carbon 
of the solution from which the material of the diamond crystals was 
derived, from which it resulted that growth (due to supersaturation) 
and reabsorbtion (due to incomplete saturation) alternated in the 
formation period of the great majority of the individuals in a way 
that thus far has not been recorded as so nearly universal for any 
other mineral species.? 
t Der Diamant, Heidelberg, 1911. 
2 My examination of numerous heavy residues containing zircon and monazite 
from granites and gneisses shows that these minerals are more frequently rounded 
from reabsorption than sharp-cut. The same remark can be made regarding the 
magnetite and ilmenite grains that occur in so many eruptive rocks. 
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