ABSTRACT OF PROCEEDINGS. ix, 
A vote of thanks was passed to the retiring President, 
and Prof. T. P. ANDERSON STUART, M.D., LL.D., was installed 
as President for the ensuing year. 
Prof. STUART thanked the members for the honour con- 
ferred upon him. 
EXHIBIT. 
The Government Geologist, Mr. HK. F. PITTMAN exhibited 
a specimen of diamond in the matrix. The specimen was 
found by Messrs. Pike and O’Donnell, in their claim at 
Oakey Creek, near Inverell. The diamond is a small one, 
weighing about one-third carat, and the material in which 
it is embedded is an igneous rock known as dolerite. The 
dolerite occurs at Oakey Creek as a pipe or dyke, and the 
Specimen is of special interest as throwing some light upon 
the question of the origin of the diamond; for it is a fair 
assumption that the gem was actually formed in the dolerite 
when the latter was cooling or solidifying from the molten 
state. The origin of diamonds has for many years been a 
subject of controversy amongst scientific men. As is well 
known, the world’s supply of diamonds is obtained chiefly 
from South Africa. The stones were at first found there in 
alluvial deposits formed of river gravels, but were ulti- 
mately traced back to a bluish-green rock, which proved 
to be a volcanic agglomerate filling the pipes of old vol- 
canoes. The diamonds were found scattered irregularly 
through this agglomerate locally known as “‘ blue-ground,”’ 
and for some time it was thought that this was the actual 
matrix of the diamond. Hragments of a crystalline rock, 
known as eclogite, are however, found in the agglomerate, 
and ultimately Professor BONNEY, who has done a great 
deal of work in investigating the origin of diamonds, 
announced that in his opinion the eclogite was the actual 
Matrix of the diamond, but that the eclogite occurred in 
the volcanic pipes in the form of water-worn pebbles, 
which had probably been derived from a bed of conglomerate 
