BRAZIL'S BLACK DIAMONDS.

Oamaru Mail, Volume XXXVIII, Issue 10592, 22 October 1910, Page 3 (Supplement)

BRAZIL'S BLACK DIAMONDS.

1 The term "black diamonds" is sometimes jokingly applied t<> ordinnry coal which we bum in our furnaces, but the real black diamonds of commerce are among the unique mineral products of the world, and they serve a purpose in the industrial world that makes them oi great value. • The'black diamonds arc pure carbon, and ~vet m no outwaid appearance resemble the diamonds which wo are accii.stomcd to wear as ornaments'. They are slightly "harder than the crystal or gem diamonds, and, in fact, about the hardest substance known. Black diamonds or carbons are among the greatest curiosities of the mineral kingdom. They arc without crystalline foini, and are found in irregular pieces tanging in Vizo ftom half a carat to three 'hundred, four hundred, "or five hundred canits. Thc\\ aie dark gray, black, or brownish m color, and opaque. Tlio real diamond ol the jewelloiy trade is also pnro carbon, biu Lianslucent and crystalline m form. Two objects so alike in composition, sa\s Ooorgo 10. AValsh in tlio Scientific Amciic.in, could not bo found so opposite in appeal ance as those two forms of carbon. Another peculiar thing about the blacky diamonds is that they are found only in one locality in tlio world. They conic from a very small section in Brazil, not more than two hundred and tw ontj-five miles squaie m area. Out"iCio or tins limited ten ltorv no pure black diiimouds have ever been found. In the Brazilian black-diamond fields tin* natives make good wages diving in I the rivet-beds for„tlicin, and recover them iloin the gra\el and washings of tlio rivors. What peculiar fieak oi nature caused the deposition oi the black diamonds in this section" of tlie world, and nowhere else, \a one ol the in\stories which science has failed to explain, None of them haa been found in the great Kimbeilc;, diamond regions, where the crystal lot m ol diamonds ha\e lor so long been mined, and likewise no lino specinu ns of the gem diamond hnvo been iomid in the Mimkili.ui black-diamond holds.

The whole origin of the black diamonds is therefore' a scientific enigma. Naturally the. question is raised,' "Of what use is a, black diamond?" No one would care to wear one of these diamonds, which resembles a piece of coal more than a leal diamond; and so far no. one has popularised 'the black gems as the black pearl has been. Nevertheless, tlie black diamonds servo a most important and useful function in . the industrial world.

This pure black carbon is not.only harder than the real diamond, but tougher, and not so brittle as the gem. Consequently it is of great value" for many mechanical purposes, and particularly for boring with diamond drills. In diamond drilling" the tips of the drills are studded with carbon.or black diamonds, and when the borea are deep the pit.ssnre is so great that the gem diamonds would bo crushed in thoprocec3,.bnt the carbon resists this, continued pressure, and slowly onts i down .into the rocks; In diamond drill work the carbon is sot in circular pieces of soft steel or iron, called bits, and tii.fie b'ts are attached to' tubing.

Armed with these black diamond teeth, the drills push their way down under severe pressure to a depth' of five thousand or six thousand feet, cutting through the-_ hardest kind of rock. Sov.'.e black diamonds are much harder . th:-:!' cabers, and there is no way to daiairnine by the color tiie difference' in the degree of toughness. Other and nxre expensive tests are employed*black diamonds of pure carboir are not by any means cheap, and the owners of the mines in Braidl,'where, they, are gathered are making a-good tiling out of their monopoly. "'Th. the hurt thirty yoa'rsjtho prices of black diamonds have ' advanced from live dollars to nearly eighty-five dollars a carat, and the tendency is still upward. The arming of a drill with diamond points is thus a rather expensive matter. Usually avsct of eight stones are placed in the head of a single drill. If each diamond weighs only three and one-half carats, flip total, cost at eighty-five dollars a carat would ha about 'two thousand three hundred and eighty dollars "for a single bit. So the black diamond, even when employed for mechanical purposes, is not far below the white, one in merit. "