70 GENERAL CHARACTERS OF PRECIOUS STONES 



of which the locality was not certainly known, was for this reason assumed to have come 

 from the " Orient." A remnant of this belief still lingers in the application of the terms 

 " oriental " to the more valuable, and " occidental " to less valuable stones. It has now 

 long been known that the habitat of the finest of precious stones is by no means confined 

 to the " Orient " and hot countries, such as India, Ceylon, Burma, Siam, Brazil, Colombia, 

 &c., but that equally fine stones may also be found in North America, the Urals, and other 

 Northern Countries. The terms" oriental" and "occidental," as now applied, have no 

 longer a geographical signification, but refer simply to the quality of the stones to which 

 they may be applied. Thus to distinguish cymophane from the more common quartz-cat's- 

 eye" it is termed " oriental cat's-eye " ; in the same way yellow sapphire is known as 

 " oriental topaz," and yellow quartz as " occidental topaz." The various localities in which 

 precious stones are and have been found will be considered in detail, along with the special 

 description of each precious stone. 



II. APPLICATIONS OF PRECIOUS STONES. 



The use to which a precious stone is put depends in the first place on its appearance, 

 and in the second on the hardness it possesses. Should it possess beauty of appearance 

 combined with a fair degree of hardness, it may be used as a personal ornament, while if it 

 possesses hardness alone, there are various technical purposes it may serve. 



A. TECHNICAL APPLICATIONS. 



The technical applications of precious stones are not numerous, and need be but briefly 

 mentioned here. 



Since the year 1700 the pivot-bearings of watches and delicate chronometers have been 

 made of some hard precious stone, since this material will best withstand the continual wear 

 of the steel axis. The stones commonly used for this purpose are known as " rubies," but 

 are in reality chrysoberyl, topaz, spinel, or indeed any stone the hardness of which is greater 

 than that of steel. The true ruby would of course answer this purpose, but a stone so 

 valuable for ornamental purposes would naturally not be used when cheaper substitutes are 

 available. Any precious stone which has the required degree of hardness, and which from 

 cloudiness, opacity, or any such blemish, is unsuitable for use as a gem, may be utilised for 

 the purpose. 



The pivot-supports of other delicate instruments, such as balances, &c., are made of 

 agate or some other hard stone ; by this means the wear is reduced to a minimum, and the 

 delicacy of the instrument preserved unimpaired for long periods. In the manufacture of 

 very fine gold and silver wires, the hole through which the wire is drawn is usually made 

 in some hard precious stone ; this will withstand the continued friction, and thus avoid the 

 possibility of gradual increase in the diameter of the hole, and consequently in that of the 

 wire. Tools used in polishing metals and for similar purposes are also made of hard stones, 

 preferably of agate. 



Those precious stones which have the greatest technical importance as abrasive agents 

 are naturally those which are at the same time the hardest of stones, namely, diamond and 

 corundum. For such purposes the latter is used in its impurest state, when it is known as 



