The DeLamar nugget. [volume] (DeLamar, Idaho) 1891-1900, 1893-03-11
The Occurrence of Diamonds.

The following, written for the Min
ing and Scientific Press, win BE- found
ofinterest to Owyhee people who will
be prospecting on Rabbit creek next
spring
"The exhibition of rough diamonds
in the exhibit of the State Mining Blu
reau at the Mechanics Fair just closed
in San Francisco attracted great deal
of attention, and was the cause of much
comment and inquiry, particularly
among mining men.
1t is with view to presenting some
of their most common physical cbarac-
taristics aud the conditions under which
they occur that this article is written.
1t may be that miners whose field of OPP
GRAFTON is in the placer mining region
may by closer observation be led to the
discovery of more of these rare and val
liable stones.
In the first place very common idea
that "Calfornia diamonds" is synony-
nous with rock crystal, which is trans
parent variety Of quartz, must be laid
aside. A California diamond is as much
gem as those found 10 South Africa,
India or Brazil. They are similar in
chemical composition. hardness, and
every other feature, and a clear or first
water diamond, free from flaw and of a
given weight, is just as valuable as
similar stone from the great Kimberley
field in South Africa.
In the tailiugs of mills crushing ce-
mented auriferons gravel in California
the fragments of diamonds have been
found, which is positive indication
that these precious stones may be found
in the old river channels as well as in
the more recent superficial gravel de-
posits-
The diamond is usually found in the
form of an octahrdren. That is crys-
tai having eight faces. These faces are
triangular and are arranged in the form
of two pyramids placed base to base. 1t
is an exceedingly hard mineral, in fact
the hardest of all known substances. In
the scale of hardness of minerals it
stands at the top-No. 10. Quartz is No.
and scratches glass. Topaz is No s.,
cutting quartz without difficulty. Sap
phire or corundum (emery) is No. g.
The diamond is also very heavy
stone, having specific gravity of 1925
as compared with quartz at go. In
color it has wide range, having been
found in all the colors of the spectrum.
Ordinarily, however, it is Whit yellow
brown or colorless, and more rarely rose
red, red, blne ana green.
About 50 per cent of the diamonds
now mined are from the Kimberley
fields in South Africa.
The hardness is the best test. if CO.
rnndum will not scratch it, aud if dla-
mond will not scratch the specimen the
probability is, that it is diamond.
In the United States diamonds are
found in two widely separated locali-
ties. viz, along the eastern base OF the
Alleghany range. from Virginia to Geor-
ola. and, in the West, along the west
err base of the Sierra Nevada, through
northern California to Oregon.
In both cases the diamonds are found
in gravel with loose earth, and are asso-
ciated with garnets and iron sands and
less common minerals and more par
ticularly with gold.
The diamonds are undoubtedly de-
rived from the crystalline rocks OF the
noun aims. A rock which appears &c
occur in several diamond producing re-
gions is called itacolumine. This ~
sandstone which splits off in slabs IKE
! hagstont 8, and contains scales OF mica
The peculiarly of this rock is, that II
will bend somewhat before breaking
and, il the pressure is removed, Will re-
sumo its former shape, being therefore
elastic.
| The most common rock in America To-
t calities, and also in Brazil and India II
5 granite. All authorities do not agree
, that the flexible sandstone Is the tru'
matrix of the diamond.
In South Africa, where the create
number of diamonds are found, an'
those of greatest value, the formation u
/, shale, containing considerable amour
. of car bon ; in fact so much that "hel
ignited the shale will burn.
Through this deposit of carbonaceou
sbale has burst mass of eruptive ROCK
, known tc geologists as peridotite' L
seems that the diamonds have formed
|, from the carbon of the shale by the In
tense heat. and, doubtless, vapors AM
f gases accompanying the eruption of thi
volcanic rock. Peridotte is the nam
of division of rocks consisting Target,
of divine.
Observe the black lava found on tn
lase,tO IF Nauada and California and il