TRANSLUCENT AND OPAQUE STONES 577 



embraces five divisions, into which fall stones of different specific gravities. The mam 

 gi'oups are : 



1. White, faintlycoloured, and grey stones. 



2. Blue stones. 



3. Green stones. 



4. Black stones. 



5. Yellow and brown stones. 



6. Eoae-red, red, and lilac stones. 



7. Stones exhibiting more than one colour. 



8. Stones with metallic lustre. 



1. WHITE, FAINTLY COLOURED, AND GBEY STONES. 



The stones of this group are distinguished by their specific gravity. 



Jadeite has almost exactly the specific gravity of liquid No. 2, and nephrite that of 

 liquid No. 3, so that they remain suspended in these respective liquids, or in some cases 

 slowly sink. Cut jadeite and nephrite can usually be distinguished by the difference in 

 specific gi'avity, and sometimes also by a difference in hardness. Rough specimens may be 

 distinguished by the difference in fusibility, for fine splinters of jadeite fuse even in an 

 ordinary candle-flame without the application of the blowpipe. 



Chalcedony is both harder and heavier than opal, and glass is invariably softer than 

 chalcedony and heavier than opal. 



2. BLUE STONES. 



Chessylite is distinguished from all other blue stones by its very dark colour, high 

 specific gravity, low hardness, and by the fact that it effervesces when brought into contact 

 with a drop of hydrochloric acid. 



Lazulite and turquoise, and specially turquoise, are ab\ays lighter in colour than 

 chessvlite, and turquoise is never very brilliant. The difference in specific gravity is 

 sufficient to di,stinguish these tAvo stones one from another, and the characters which 



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