413 Mineraloyical Notices. 



reactions of copper and iron. M. Plattner obtained on analysis 



the following results : — 



Sulphur 32-222 



Arsenic 17-599 



Antimony 1-613 



Copper 47-205 



Iron 0'565 



Zinc 0-228 



SUver 0-017 



99-449 



This mineral is therefore essentially composed of a sulpho- 

 arseniuret of copper, in which the relation of the equivalents of 

 sulphur, arsenic and copper, is almost exactly as 8 : 1 : 6. Such 

 a relation, supposing the arsenic to be in the state of trisulphuret, 

 requires the rather complicated formula 8Cu S, As S^ + 2Cu^ S, 

 As S' ; but supposing the arsenic to exist in the state of penta- 

 sulphuret, we have the more simple formula 3Cu^ S + As S^. 



EMERYLITE. BY DR. J. LAWRENCE SMITH. 

 [Silliman's American Journal, January 1851.] 



This mineral, Avhich belongs to the family of micas, is lamellar 

 like mica; the plates are easily separated, and possess a little 

 elasticity. Sometimes it is in the form of a mass composed of 

 very small pearly scales, which are very friable, resembling some 

 species of talc. The plates are commonly convex and concave, 

 grouped in such a manner as to form a triangular prism. It is 

 also found massive with a micaceous structm-e, but with an irre- 

 gular fractui-e ; the aspect of this variety is waxy : it comes from 

 Gumuch-dagh. The crystalline form is difficult to determine; 

 but to judge from the streaks on the surface, and the imperfect 

 cleavage in two directions, it would appear to belong to an 

 oblique rhombic prism. 



Its colour is white and lustre silvery ; the hardness taken on 

 a specimen from the Island of Nicaria is from 4 to 4-5. The 

 specific gravity taken on ten specimens varies from 2-80 to 3-09 ; 

 this difference is not remarkable in a lamellated mineral. It is 

 not attacked by acids ; heated before the blo^\q)ipe it emits a 

 bright light, and melts vat\\ great difficulty on the edges, which 

 assume a blue colour if touched \A-ith the nitrate of cobalt and 

 reheated. Heated in a tube it furnishes water, frequently having 

 an acid reaction due to fluoric acid. 



The composition of several specimens subjected to analysis is 

 as follows : — 



