On the Mineral Cyjprusite. By Julien Dehy. 187 



the outcrop ("gossan," as Cornisli miners would call it) of the 

 copper lodes so celebrated in the times of remote antiquity. A 

 further investigation has led me to the belief that, at a certain 

 depth, the cyprusite is replaced by iron pyrites, and that lower 

 down still these pyrites become cupreous, and that these constituted 

 a portion of the mineral which was worked by the Phoenicians, 

 Greeks, and Komans in the island of Cyprus. 



I observed in several places below the cyprusite the efflo- 

 rescences mentioned by Dr. Eeinsch; their composition is as 

 follows : — 



Insoluble in water ., 4*88 per cent. 



Copper 0*45 „ 



Iron none 



Alumina 17 '70 „ 



Sulphuric Acid 35 • 19 „ 



Water of crystallization 39-00 „ 



Total .. ,. 97-22 „ 



This mineral had a whitish, slightly greenish tinge and semi- 

 crystalline structure, and looked exactly like weathered sulphate of 

 iron. It consists, however, essentially of sulphate of alumina 

 (nearly 2 AI2 O3 . 5 SO3 + 25 H2 0) coloured by copper. 



The cyprusite was submitted for complete analysis to my friend 

 Henry Fulton, Esq., the late well-known and able chemist to the 

 Kio Tinto Company, now of Aguilas, Spain, to whose kindness I 

 am indebted for the greater part of the chemical determinations 

 in the present communication. 



A first experiment consisted in simply drying the mineral to 

 from 100 to 115 degrees Centigrade, when slight vapours which 

 coloured litmus blue were given off. Another portion was next 

 submitted to a red heat in a platinum crucible for six hours, until 

 the fumes ceased to colour litmus paper, when it was found by 

 analysis that 17 "19 per cent, of sulphuric acid had been given off. 

 At the same time the colour had passed from yellow through bright 

 red to a dark purple. 



The average of several carefully made analyses of the yellow or 

 typical and most abundant variety of cyprusite, after separation of 

 the insoluble portion, which, as we shall see, does not enter into 

 the chemical composition of the mineral, was found to be : — 



Ferric oxide, Fcj O3 49 - 68 per cent. 



Alumina, AI2 O3 3-89 „ 



Sulphuric acid, SO3 35-34 „ 



Water, H2O 11-06 „ 



Total ,. .. 99-97 



The mineral is thus seen to constitute a normal sulphate of 

 alumina with anhydrous ferric tribasic sulphate, the whole having 



o 2 



