266 J. MILNE CURRAN. 
_ *Nores ON THE DISCRIMINATION OF GEMS. 
In view of the fact that this paper will be read by prospectors 
and others in far-off districts, I venture to add a few notes on the 
discrimination of gems. : 
In my own experience, I find it a common occurrence to have 
lustrous quartz crystals mistaken for diamonds; and numbers of 
practical men fail to distinguish between topaz and quartz. 
‘Another every-day difficulty is to discriminate between white 
zircon and diamond. On these points, therefore, I append some 
notes, intended for those who are so situated as not to have the 
methods and resources of a laboratory at their disposal. 
Laboratory methods for the determination of gems have now 
reached great perfection, so much so that the mineralogist is 
not now forced to determine the hardness of a gem, as a necessary 
process in establishing its specific identity. Mr. Lewis Abbot, 
says, in one of his lectures, that ‘““we can begin by dismissing 
hardness as a character which it is really necessary to determine, 
except to identify the diamond or to distinguish a real stone from 
a paste; here I know I shall earn a rebuke from the orthodox 
mineralogist, who, in order to pursue the study of what should be 
a peaceful science, arms himself with a knife and proceeds to 
scratch everything which he comes across.” 
In the laboratory where accurate observation is possible, the 
optical properties and specific gravity will give data sufficient to 
determine most gems. The use of heavy solutions that float many 
gem-stones is now a recognised method. The reflecting goniometer, 
the polariscope, the stauroscope, the dichroscope, and the total 
reflectometer are also used to discriminate between gems. The 
prospector, however, cannot avail himself of the precision that these 
instruments make possible, and he is compelled to fall back on the 
hardness, colour, fusibility, specific gravity, and perhaps the 
crystalline form of supposed gem stones. | 
Diamonds.— Zircon is most commonly taken for diamond by 
prospectors. The parcels of diamonds sent from Bingara very 
