77 



TAB. CXLI. 



FERRUM Cupreo-arseniatum. 

 Cupreous Arseniate of Iron. 



Class 3. Metals, Order 1 . Homogeneous. 

 Gen. 7. Iron. Spec. Arseniate. 



Far. Cupreous. 



Spec. Char. Iron, Copper, and Arsenic Acid in 

 combination. 



Syn. Cupreous Arseniate of Iron. Bournon and 

 Ckenevix^ Phil. Trans, for 1801. 



This substance, which is rare in Cornwall, we understand 

 has been brought from Siberia by Professor Pallas, accord- 

 ing to Mr. Chenevix, to whom we are obliged for the 

 analysis of it, and to Count Bournon for the most ac- 

 curate account of its crystallization, which agrees with 

 our specimens. It is found in the Muttrel mine along 

 with the cubic Arseniate of Iron. The crystals are always 

 small, generally clustered, more or less in bundles or con- 

 fused. The individuals form rhomboidal prisms having 

 the two opposite angles very obtuse; and consequently the 

 two others are very acute, terminating with four scalene 

 triangular faces, fixed lower on the acute angles than on 

 the obtuse ones. We cannot be certain that the angle bear- 

 ing upon the obtuse side of the pyramid is not a right angle : 

 see the geometrical figure. The upper specimen is a largish 



