158 



PHYSIOGRAPHY. 



Red Lead-Ore. 



Secondary forms. 1. The primary, having the obtuse 

 terminal edges replaced by single planes, and then so far 

 extended as to obliterate the terminal plane ; the lateral 

 edges of the prisms being replaced by tangent planes. 



2. The same as the above, having in addition the acute 

 terminal edges replaced, so as to impart four-sided sum- 

 mits to the crystals. 



3. The same as 2, with the exception of having the ob- 

 lique edges of the prism replaced, instead of the lateral, as in 



Fig. 379. 



M 



Cleavage, parallel to the primary, tolerably distinct: less 

 so to the bases, than to the sides of the prism. Fracture 

 small conchoidal, uneven. Surface, M streaked longitudi- 

 nally. The faces mostly smooth and shining. 



Lustre adamantine. Color various shades of hyacinth- 

 red. Streak orange-yellow. Translucent. 



Sectile. Hardness =2-5 . . . 3-0. Sp. gr. 6-004. 



Compound Varieties. Massive : composition imperfectly 

 columnar, or granular. 



1. Before the blow-pipe, it becomes black and decrepitates, if quickly 

 heated; it may be melted, however, into a shining slag, containing glob- 

 ules of metallic lead. It colors glass of borax green, is soluble without 

 effervescence in nitric acid, and affords a yellow solution in that acid. 



