The Chemistry, Properties and Tests of Precious Stones

ific G

n cork, the cork will sink in it as does iron in water; in the second instance, if we change the liquid to one heavier than iron, the iron will float on it as does cork on water, and exactly as an ordinary flat-iron will float on quicksilver, bobbing up and down like a cork in a tumbler of water. If, therefore, solutions of known but varying densities are compounded, it is possible to tell almost to exactitude the specific gravity of any stone dropped into them, by the position they assume. Thus, if we take a solution of pure methylene iodide, which has a specific gravity of 3.2981, and into this drop a few stones selected indiscriminately, the effect will be curious: first, some will sin

which is the heaviest known, will float in it. For use, the mixture should be slightly warmed till it runs thin and clear; this is necessary, because at 60° (taking this as ordinary atmospheric temperature) it is a stiff mass. A lighter liquid is a mixture of iodide of mercury in iodide of potassium, but this is such an extremely corrosive and dangerous mixture, that the more common solution is one in which methylene iodide is saturated with a mixture of iodoform until it shows a specific g

e with accuracy if any stone is what it is supposed to be, and classify it correctly by its mere floating or sinking when placed in these liquids. Beginning then with the pure double nitrate of silver an

hich have a specific

.70 and u

" 3.50

" 3.00

" 2.50

" 2.00

- - un

elling them to float on its surface; commencing with the heaviest and

4.7963 and over 4.70; in this group is placed zi

ecific gravity lies betw

varieties. See

1 and occasio

.073 "

e 4.049

um 3.9

Ruby

toid

olite

10 and occasi

ecific gravity lies betw

(averag

689 and occasi

3.614

3.609

te 3.60

3.502

3.500

pecific gravity lies be

13 and occasi

3.400

3.360

and occasio

e 3.346

3.334

te 3.316

.300 "

ite

ite

tase

side

ne (yell

usite

ite

(Blue and V

ne (Gree

ed)

30 and occasi

ase

31 and occasi

e (Colour

e (Blush

k) 3.024 and occ

rite

ecific gravity lies betw

kite

oise

and occasion

ine 2.7

dorit

ald

tz 2

opras

er 2

hyst

tone

ine

erite

te

98 and occasio

aria

.521 and occas

ecific gravity lies betw

0 and occasio

lazuli

vite

according to

pal) 2.21

hose specific gra

1.

er

arranged in their respecti

is is especially appreciated when it is remembered that so far science has been unable (except in very rare instances of no importance) to manufacture any stone of the same colour as the genuine and at the same time of the same specific gravity. Either the colour and characteristics suffer in obtaining the required weight or density, or if the colour and other properties of an artificial stone are made closely to resemble the real, then the specific gravity is so greatly different, either more or less, as at once to stamp the jewel as false. In the very few exceptions where ch