71 



TAB. CCCXLL 



PLUMBUM sulphatum. 

 Sulphate of Lead. 



Div. 1. Crystallized. 



These peculiar green Lead Ores have created some con- 

 fusion among Mineralogists, from their having been con- 

 sidered by several as Molybdates of Lead*, which, I be- 

 lieve, we have not yet found in this country. I was fa- 

 voured with the present specimen from Wanlock-head by 

 G. Laing, Esq., who has so often kindly given me occasion 

 to mention him in the course of this work. 



The Crystal is a long rectangular prism placed upon one 

 of its sides. Two of its faces, the upper and lower, are 

 primitives ; the larger two terminal faces are also primitives, 

 being the sides of a rhomboidal prism ; the middle of the 

 three smaller faces is on the acute solid angle, the other 

 two are on the succeeding, or the thus newly made solid 

 angles. We find this to be the same primitive as tab. 153, 

 which upon further examination proves to be also a Sulphate. 

 Its insolubility in hot Nitric Acid diluted, confirms its 

 being a Sulphate, besides other trials, by some of which 

 we are led to suspect a small portion of Muriatic Acid ; but 

 we had too small a morsel to try it perfectly f. 



The green hue of the present specimen may depend upon 

 Oxide of Iron, or some foreign ingredient. 



* Found in Carinthia. 



f It would be very desirable that Mr. Gregor, Dr. Wollaston, or some such 

 person, in whom we may place confidence, would examine these substances. 



