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XXX. — On Std-phuret of Cadmium, or Greenockite, a new Mineral. By Arthur 



CoNNELL, Esq., F. B. S. E. 



(Read 16th March 1840.) 



This mineral is found embedded in small crystals in prehnite, at Bishop- 

 town, in Renfrewshire. It had been long supposed by mineralogists to be a va- 

 riety of zinc-blende ; but it was first distinguished from that mineral by Lord 

 Greenock, who communicated his opinion to Professor Jameson ; and two small 

 crystals, together less than a grain in weight, were sent to me for chemical exa- 

 mination by the latter, who concun'ed in the supposition that it was a new mi- 

 neral. 



The crystals sent appeared to be six-sided pyramids, having the faces trans- 

 versely streaked. Their colour was wine-yellow. Fracture, conchoidal. Lustre, 

 shining or splendent, and vitreous. Hardness about that of calcareous spar; 

 streak orange-red ; semitransparent. 



A small fragment heated in a glass-tube acquired a beautiful deep carmine- 

 red colour, and on cooling recovered its yellow tint. At a red heat it did not fuse 

 nor volatilize. These reactions at once distinguished the mineral from the native 

 sulphurets of arsenic, to which it bore some external resemblance. In an open 

 glass-tube, the appearances were exactly the same, even when urged by the blow- 

 pipe ; it became as before deep red, and on cooling recovered its yellow colour, 

 retaining its lustre and transparency. When a somewhat larger fragment was 

 heated in a glass-tube, it decrepitated violently before assuming the red tint, but 

 no evolution of vapour was observed ; and when the particles into which it se- 

 parated were collected together into one place, and heated tiU almost black over 

 a spirit-lamp, and then shifted into a different part of the tube, every depth of 

 tint of red was observed according to the temperature. 



In powder it was readily soluble in muriatic acid, by the aid of heat, ex- 

 haling a strong smell of sulphuretted hydrogen. Carbonate of soda caused a 

 white precipitate, dissolved by ammonia. The muriatic solution by evaporation 

 afforded a white prismatic crystallization, not deliquescing in an ordinary atmo- 

 sphere. This character distinguished the mineral from zinc-blende, with which 

 the previous reactions had closely corresponded, and suggested the idea that it 

 might be sulphuret of cadmium, a supposition farther strengthened by finding the 



VOL. XIV. PART II. 5 X 



