PHYSIOGRAPHY. 149 



Corneous Lead Corundum. 



CORNEOUS LEAD. Kerasine Lead-Baryte. 



Primary form. Right square prism. 



Secondary form. The primary form having its lateral 

 and terminal edges replaced by single planes. 



Cleavage, parallel to the lateral planes of the primary ; 

 cross fracture conchoidal. 



Lustre adamantine. Color white and pale tints of grey, 

 yellow and green. Streak white. Transparent to trans- 

 lucent. 



Sectile. Hardness below 3-0. Sp. gr. =6-056. 



1. Before the blow-pipe, it melts quickly into a yellow globule, which 

 becomes white and crystallizes upon the surface, when cooling. Upon 

 charcoal, it is reduced. 



2. Analysis. 



By KLAPKOTH. By BERZELIUS, 



I'r. Mendip. 



Oxide of lead 85-5 . Lead 25-85 



Muriatic acid 8-5 . Oxide of lead 57-07 



Carbonic acid 6-0 . Carbonate of lead 6-25 



Chlonne 00 , 8-84 



Silica 00 . V46 



Water 0-0 . 0-54 



3. It is found at the Mendip hills in Somersetshire, at Matlock in Der- 

 byshire, Hausbaden near Badeuweiler in Germany, and in the United 

 States at Southampton, (Mass.) 



CORUNDUM. Rhombohedral Corundum, 

 MOHS. 



Primary form. Rhomboid. P on P'=86 4'. 



Secondary forms. 1. Regular six-sided prism. 2. The 

 same, having the terminal edges replaced. 3. Dodecahe- 

 dron with isosceles-triangular faces, the upper pyramid in- 

 clining to the lower under 121 34'. 4. The same, with 

 the summits replaced by single planes. 



13* 



