101 



TAB. CLIII. 



PLUMBUM carbonatum primitivum. 

 Primitive Crystallized Carbonate of Lead. 



Class 3. Metals. Order I. Homogeneous. 

 Gen. 15. Lead. Spec. A. Carbonate of Lead. 



Div. 1. Crystallized. 



1 his specimen is a great curiosity, as it does not seem to 

 have been before known that Carbonate of Lead crystallized 

 in rhomboidal prisms. Haiiy seemed to think the octaedron 

 to be the primitive figure ; indeed we have been able in 

 some specimens to trace all but four of his fractures ; this 

 however appears to be preferable, as it bears some analogy 

 to Sulphate of Barytes, which has a rhomboidal primitive 

 only differing in the angles, otherwise often producing 

 similar modifications, which vary according to the nature 

 of the substance, The angles of this rhomboidal prism are 

 76° and 104°; the laminae are very distinct on all the faces. 

 Carbonate of Lead, when we find it so nearly resembling 

 this substance, may soon be discovered by the help of the 

 blowpipe in procuring a little globule, of Lead from it on 

 Charcoal. They both form a nearly opaque glass ; but if 

 the heat is continued, the one will of course be reduced to 

 Lead, and the other will remain unaltered. 



VOL, II. k 



