The Chemistry, Properties and Tests of Precious Stones

when dealing with the stones seriatim, it is necessary to enquire into those particulars of origin which are c

f the rarer metals, such as platinum, gold, etc., or any of their compounds, but are composed entirely of the common elements and their derivatives, especially of those elements contained in the upper crust of the earth, and this notwithstanding the fact that gems are often found deep down in the earth. This is very significant, and points to the co

e comes when it enters perhaps a division-plane in some rock, or some such cavity, and is unable to get away. The hollow becomes filled with water, which is slowly more and more charged with the salts brought down, till saturated; then super-saturated, so that the salts become precipitated, or perha

behaviour of some well-known salts, under different conditions of temperature, what

ne easy to obtain for experiment, is the sul

does not exceed 60° F., and at this temperature a super-saturated solution may easily be made. But if the water is

ithout heating, is dropped a small crystal of the same salt, there will be caused a rise in temperature, and the whole will then crystallise

, and after being subjected for a period, extending to ages, to the washings of moisture, the contact of its containing bed (its later matrix), the action of the changes in the temperature of the earth in its vicinity, it em

as acted on a portion of the rock on which it rested, absorbing the rock, and, as it were, replacing it by its own substance. This is evidenced in cases w

r it is obvious that the same salt-charged aqueous solution which undergoes change in and on iro

stones-which fact may advisedly be repeated. It is, of course, to be expected that beryllium will be found in the emerald, since it is under the species beryl, and zirconium in zircon; but such instances are t

stallised carbon; a different form from graphite, it is true, but, nevertheless, pure carbon and nothing else. Theref

t their chemical constituents are exactly the same, the difference being one of colour only. These have two elements, oxygen and alu

n of water, which renders it easily liable to destruction, as we shall see later. It is a combination of alumin

the opal, amethyst, agate, rock-crystal, and the like, as the best known examples, whilst oxygen appears also mostly in the form of oxides, in chrysoberyl, spinel, and the like. This silica group is extremely interesting, f

are the carbonate series, containing much carbonic acid, and, as may be expected, a considerable proportion of water in t

he origin of the formation of all precious stones; and all the precious stones known have, when analysed, been found to be almost exclusively composed of upper-earth

und liquids, with time and pressure, form metallic min

ides; in cases where the metalliferous ores or the metallic elements enter into composition with the halogens-bromine, chlorine, fluorine, and iodine-in all these, prec

s and earth being transformed into metalliferous ores by the same means-precious stones (or that portion of them ranking as jewels or gems) must on the contrary be wholly, or almost wholly, composed of upper-earth-cr