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Chrysocolla from Cuba. 207 



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exhibits a perfect conclipidal fracture. It yields to the 

 knife, but scratches glass readily. It is brittle. Its pow- 

 der is nearly white, having a slight tint of green. It ad- 

 heres to the tongue, and absorbs water when immersed 

 in that fluid. It takes a good polish, which it preserves 

 when the surface is oiled. 



Sp. Gr. = 2.16. When a fragment of the mineral is 

 treated with carbonate of soda on charcoal before the 

 blow-pipe, it melts with effervescence, and a globule of 

 copper is obtained. A portion of the mineral being 

 powdered and treated with muriatic acid, no eiferves- 

 cence took place, but oxide of copper dissolved, leaving 



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silica, insoluble, behind. 



ANALYSIS 





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A. To ascertain the quantity of water contained in 

 the mineral, 25 grains in powder were subjected to a red 

 heat in a platina capsule. It lost 8.26 grains, equal to 

 33 per cent, of water. 



B. Twenty-five grains of the powdered mineral, in a 

 glass flask, were subjected to the action of muriatic acid, 

 and the digestion w as continued 48 hours on the heated 

 sand bath, the acid being removed and renewed until it 

 ceased to dissolve any thing. The solution was then 

 diluted largely with water, and the w4iole thrown on a 

 filter, to separate the silica, which, collected, washed, 

 dried, ignited and we 

 to 30 per cent, of silica. 



C. The solution which had passed the fiUer w^ith the 

 washings of the silica was treated, while boiling hot, with 

 a hot solution of pure potash, and boiled. A dense, black 

 precipitate took place, consisting of deut-oxide of cop- 

 per, which, collected on a filter, washed, dried, ignited 



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