Burlington weekly free press. [volume] (Burlington, Vt.) 1866-1928, 1909-11-04
THE REAL BLACK DIAMOND.
1t Is Found Only in q Very Small Sec.
tlOn of Brazil.
(From the Scientific American.)

ton Of Brazil.
(From the Scientific American.)
The term black diamond" is some
times jokngly applied to ordinary coal
which we burn 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 os
great value.
The black diamonds are pure carbon,
and yet in on outward appearance re-
semble the diamonds which we are ac-
custoned to wear as ornaments They
are slightly harder than the crystal or
gem diamonds. and in fact about She
hardest substance known.
Black diamonds or carbons are among
the greatest curiosities OF the mineral
| Kingdom. They are without crystalline
form, and are found in irregular pieces
ranging in size from half carat to 800.
400 or 80 carats They are dark gray,
black or brownish in color and Opaque
The real diamond Of the jewery trade
is also pure carbon, but translucent and
crystalline In form. Two objects so alike
in composition could not be found 50
opposite in appearance as these two
forms OF carbon.
Another peculiar thing about the black
diamonds is that they are found only In
one locality IN the world The come
from a very small section in Brazil, not
more than 2o5 miles square In area. Out
side OF this limited territory no pure
black diamonds have ever been found.
In the Brazilian black diamond fields
the natives dive in the river beds for
them. and recover them from the gravel
and washings Of the rivers.
What peculiar freak Of nature caused
tho disposition Of the black diamonds in
this section Of the world and nowhere
else is one o: the mysteries which science
has failed to explain. None Of them has
been found in the great Kimberly dia-
mand regions. where the crystal form
OF diamonds have for so long been mined,
and likewise no fine specimens OF the
gem diamond have been fouid N tho
Brazilian black diamond fields.
The whole origin Of the black diamonds
is therefore a scientific enigma. Natural
ly the question is raised, "Of what use
is a black diamond" No one would
care to wear one of these diamonds.
which resembles n piece Of coal more
than real diamond, and so far no
one has popularized the black gems as
the black pearl has been. Nevertheless
the black diamonds serve most i'm
portant and useful function in the indus
trial world.
This pure black carbon is not only
harder than the real diamond. but tough
er and not so brittle rs the gem. Con-
sequenty II is Of great value for many
mechanical purposes. and particularly
for boring with diamond drills. In dia-
mond drilling the tips af the drills are
stubbed with carbon or black diamonds.
and when the bores are deep the pres
sure in so great that the gam diamonds
would be crushed in the process. but tho
carbon resists this continued pressure
and SLOWLY eats down into the rocks.
In diamond drill work the carbon is
set In circular pieces of soft steel or
iron called bits and these bits are at
tached to tubing. Armed with these
black diamond teeth the drills push their
way down under severe pressure to n
depth OF Ave thousand or six thousand
, feet. cutting through the hardest kind
| Of rock. Some black diamonds are much
harder than others and there is no way
to determine by the color the difference
in the degree OF toughness.
Black diamonds or pure carbon are
not by any means cheap, and the own
ers Of the mines in Brazil where they
are gathered are making a good thing
ont of their monopoly. In the last thirty
wears the prices of black diamonds have
advanced from $ to nearly $50 a carat,
and the tendency Is still upward. The
arming OF a drill with diamond points
is thus a rather expensive matter.
Usually set Of eight stones are placed
in the head OF single drill. II each
diamond weighs only 81. carats the To-
tai cost at SIS a carat would be about
$3.50 for a single BIT
Great as the expense is. however, It
pays. for the black diamonds are so
tough that they last a long time and
they achieve results which could not
be obtained In any other way. There
Is no known substance that can take
the place Of carbon in drills in boring for
gold. silver. copper ana other mineral
deposits. Before the black diamonds Of
Brazil were discovered 1t was impossible
to make deep borings.
When the carbon was first introduced
In our industries II was used In diamond
SAWS for cutting stones. marble and SIM
liar substances. Then the price advance
ed that the carbon was found too
costly for such use and bort was substi-
tuted for stone cutting. Bort Is really
EN- imperfect crystal or gem diamond, but
II IL too brittle for use in drills. Consc-
quently bort has taken the place of
black diamonds for stone cutting and
the latter have been restricted almost
entirely to diamond drilling purposes.
The average size Of black diamonds
used In the drills ranges from two to
five carats. hut the larger specimens
give much hotter results. They cost
more. but they last longer. Consequent
~ there is greater demand for the
larger pieces OF pure carbon and the price
10 sometimes run up to premium figures
for unusual specimens.