The morning news. [volume] (Savannah, Ga.) 1887-1900, 1899-01-11
TO IDENTIFY PRECIOUS STONES.
Hardness nnd Specific Qualities
Closely Studied.

AiDSely stunned.
From the st. Louis Globe-Democrat.
Leopold Claremont says that prospectors
and others who have not had opportunities
Of handling precious stones in the rough
often have the greatest difficulty In distin-
gushing them from one another, and dis
eliminating between gems of great value
and those comparatively worthless. 1t is
mistake to place any reliance whatever on
color as a test of a precious stone as
there is no property natural to gems which
is hck.e and unreliable as color. For
instance, If a stone be red IL is not nee
essarily ruby; nor need a white stone
be diamond; and there are yellow sap
phires, green diamonds and blue spineIs.
In the diagnosis of precious stones It is
desirable 20 apply as many tests as pos
sible. The properties most easily and most
universally Used as tests are those of hard
ness and specific gravity. The mineraIog-
list Mons devised scale of hardness con-
sisting Of twelve minerals, which forms a
recognized standard to which specimens
under examination may be compared. The
scale IS as follows: Diamond 10; sap
phire, .; topaz, 8; quartz, 4 feldspar, 6;
apatite, 3; duorspar, 4; calcite, g. rocksalt.
2; tale, l. Fragments of these minerals.
suitably mounted in little handles are ap-
piled In succession to the gem to be exam
ined, so as to attempt to scratch it, When
the gem neither scratches nor is scratched
by any member Of the SCALE the two stones
may be considered of the same hardness.
When 1t scratches the softer and ia
scratched by the harder of two test
stones some idea of its position between
them may be obtained by drawing all
three specimens, with slight pressure.
across the surface of fine, Clean hard
file, and noticing the different degrees OF
resistance to abrasion and the sound pro-
duced This operation requires to be done
with great delicacy of touch. Ii is noted
that the toughest diamonds come from
Australia, while Indian and Brazilian
stones are harder than those from the
Cape.
To obtain the specific gravity of a stone
liquids of different degrees of density are
used In which the gems either hoav or
sink according to their relative weight.
Nothing can be easier or more satisfac-
tory than this method However minute
the stone may be, il can be Identified by
its density in few moments. Supposing
there Is doubt whether a certain gem in
an aquamaraine or a chrysoberyl all that
is necessary is to place it in a tube Of
methylene iodide, together with small frag-
ment known to be aquamarine to serve
as an index. IL IL be a chrysoberyl.
which has specific gravity of 3.6, IL will
Immediately sink; IL IL be an aduamarine
which has a specific gravity of 81, 1t will
float, in which case. IL the liquid be de
luted and stirred until the index fragment
is exactly suspended the doubtful germ
also win neither float nor sink but will
remain poised beside it. But, unfortunate
ly for the general adoption of this method.
a great number of gem stones are heavier
than methylene lodide. The Dutch miner
alogst, Retgers. however, has made a
discovery which in a great measure sur
mounts this difficulty. He has found a
colorless, solid compound which melts at
a temperature far below that of boiling
water to a clear liquid five times as dense
as water and, therefore, sufficiently dense
to float any known precious stone, This
compound is a double nitrate of silver and
thallium, and possesses the remarkable
property Of mixing in any desired pro-
portion with warm water, SO that by de
luton the specific gravity may be easily
reduced. The fused mass may be reduced
in density by adding water. drop by drop.
so as to suspend in succession targoon.
carbuncle, sapphire, ruby, chrysoberyI
and spinel. The optical properties OF
precious stones form valuable means Of
identifying them, especially when cut and
polished, and there are several different
kinds of scientific instruments such as
the goniometer, the dichroscope and the
spectroscope, which can be applied for this
Durpose.