THE DETERMINATION AND DISTINGUISHING 

 OF PRECIOUS STONES 



Under the description of each precious stone mentioned in this work there will be found a 

 method of distinguishing it from precious stones of similar appearance or from imitations. 

 By the application of the tests there laid down it is possible to determine whether a 

 supposed diamond, for example, is really such, or whether it is another precious stone of 

 similar appearance, or merely a glass imitation. 



There are many cases in which the colour of a precious stone — always the first and 

 most important feature to strike the eye — offers no obvious clue to its identity. We may, 

 for example, meet with a red stone which might equally well be ruby, spinel, garnet, topaz, 

 tourmaline, fluor-spar, or even red glass. 



An experienced jeweller or mineralogist would seldom be in doubt in such a case, for 

 he would be guided by external characters such as transparency, lustre, shade of colour, &c., 

 all observable with the naked eye or with a lens. And in the case of a rough, uncut stone 

 the identification is made more easily by the evidence afforded by the crystalline form of 

 the stone, the character of its fractured surface, and the presence or absence of cleavage, 

 evidence which in skilful hands usually points to a correct conclusion. 



Glass can frequently be distinguished from genuine precious stones by the fact that it 

 is warmer to the touch, and that, when breathed upon, it receives a film of moisture more 

 easily, and retains it for a longer period, than do precious stones. 



In cases where the more obvious characters of a stone are insufficient to establish its 

 identity one has to fall back on its less conspicuous features, the observation of which may 

 require the aid of some specially designed instruments and appliances. 



These instruments and appliances to be of any practical value must be simple and 

 substantial, as cheap as possible, and such that determinations made with their aid can be 

 as well performed by the working jeweller as by a trained mineralogist. The methods 

 adopted for the determination should be such as can be employed without injury to the 

 stone, especially when the latter is cut, the avoidance of small surface injuries in uncut 

 stones being of less importance. If the method of determination can be applied to mounted 

 stones so much the better, but in many cases this is impossible, and gems for which large 

 sums are asked should always be purchased unmounted. 



The features which best fulfil the requirements outlined above are the optical characters 

 and the specific gravity. The observation of these features is therefore a matter of 

 considerable importance, and has been dealt with in detail in Part I. of this work. It is 

 proposed here to recapitulate briefly the main facts of the subject, and for details to refer 

 the reader to Part I., or to the special description of each precious stone given in Part II. 



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