The Occurrence and Distribution of Diamonds in India. 555 
The issue of the “Manual of the Geology of India” last 
year places the work of the Survey and our present knowledge of 
Indian geology in a more accessible and condensed form than it 
possessed when scattered through the now voluminous publica- 
tions of the Survey. It is to be hoped that writers of geological 
text-books will in the future refer to it for their facts, rather 
than to the old sources of information, and that we shall never 
again see the “diamond sandstone,” so called, classed as an Indian 
representative of the European Oolite. 
Among the authorities quoted by Dr. Carter in reference to 
the diamond-bearing strata, the following are the principal :— 
Heyne, Jacquemont, Franklin, Voysey, and Newbold. 
Some of these, especially Heyne, maintained that the diamond 
occurred only in a superficial recent conglomerate, formed of a 
great variety of fragments of the surrounding rocks, and resting 
indiscriminately on old rocks of different ages. Others recognised 
that in some cases the matrix of the gem was a conglomerate, 
which was a member of the clay slate formation, so called. This 
“ clay slate formation,” which included sandstones and limestones, 
and all their varieties now embraced in the Vindhyan formation, 
were considered to be the altered representatives of the Oolite, this 
being the age assigned to the coal-measures and associated plant 
and reptilian fossil-bearing sandstones. The latter were in fact 
held to constitute the unaltered portion of the rocks of the same 
period. The work of the Survey has demonstrated that this 
clay slate, or diamond sandstone, or Vindhyan formation is 
separated by a wide break in time from the fossil-bearing rocks, 
being itself, so far as is known, absolutely azoic, and occupying 
a position in the geological sequence, which may range from 
Lower Silurian to Carboniferous. 
Further reference to the fossiliferous rocks will therefore be 
unnecessary in this paper.* 
Dr. Carter arrived at the conclusion that the diamond-bearing 
conglomerates described by various authorities, occurred, at least, 
in the neighbourhood of, if they did not constitute members 
of, the Oolite formation. If for Oolite the term Vindhyan be 
* They will be found described in my paper ‘“ On the Coal Fields and Coal Production of 
India.” 
