blende
diabase dikes, standing nearly vertical, were cut through. The tirst
one was about 26 feet thick; the other two were smaller. In the middle
of the first dike a diamond of about one-half carat weight was found
embedded in solid intrusive rock. Three more small diamonds were later
picked out of the more decomposed diabase after it had been exposed to
the weather for some time. One of these stones has corrosion hollows on
the surface tilled with portions of the hornblende diabase matrix.
These
specimens, one with the diamond still in the matrix, were exhibited
before the geological section of the British Association for the
Advancement of Science, and the mode of origin was discussed. Sir
William Crookes thought the diamonds had probably formed originally
under absolutely nonoxidizing conditions, as would be found in molten
iron. Arguments brought against Crookes's theory that the diamonds were
originally formed from molten iron were that Doctor Fried-lander, of
Berlin, had made microscopic diamonds by stirring molten olivine (not
very different in composition from the Inverell hornblende diabase)
with a graphite rod, and that the diamonds were found in the Novo-Urei
meteorite of Russia, which was composed chiefly of silicates. The
general opinion seemed to be that the hornblende basalt might well be
the original matrix of the diamond, without the necessity of assuming
deeply buried masses of metallic iron which were subsequently absorbed
by the hornblende basalt.
Consul F. W. Coding reports8
from New Castle, New South Wales, that rough diamonds have been found
lately in Queensland ranging from 1 to 5 carats in weight. The finds
have not been numerous, and since European and American merchants have
judged them to be of inferior quality exploration has not been pushed
vigorously.
Another
locality for diamonds in Australia has been reported * on the eastern
slopes of the Nandewar Range, toward Bingara, where it is said a blue
diamond was found and sold locality for £5. At Sydnev it brought £32
10s.
TASMANIA.
During
1906 a diamond is reported to have been found on the west coast of
Tasmania, at Long Plains. According to Mr. W. H. Twelve-trees,
government geologist, the presence of ultra-basic rocks and
carbonaceous shale may point to diamond-bearing rock being found in the
region. The diamond found weighed about one-eighth carat. It was an
octohedral crystal, with a peculiar greenish-yellow tint at the points.
NEW ZEALAND.
Specimens labeled "gem sands'" of Kakanuic
were collected some years ago by the late Professor Ulrich, of the
Otago School of Mines, with the idea that gems might be found
associated with these sands at some future time. Careful inquiry has
failed to discover in the Kakanui region more than a few sapphires of
indifferent quality; a jasperoid rock, containing green, yellow, and
red bands; and the "gem sands" themselves. The origin of the gem sands
has been traced
aU. S. Daily Cons. Repts. No. 2819, March 10, 1907, ^Mining Jour. (London), May 11, 1907.
^'Thompson, J. Allen, Gem sands of Kakanui: Trans, and Proc. New Zealand Inst., vol. 38, 1905 pp. 482-495.
