284 PHYSIOGRAPHY. 



Yellow Copper Pyrites Yellow Lead-Ore. 



Rather sectile. Hardness = 3-5 . . . 4-0. Sp. gr. = 

 4-169. 



Compound Varieties. Twin-crystals : face of compo- 

 sition perpendicular to a face of P, similar to the common 

 hemitrope in the regular octahedron. Globular, reniform, 

 botryoidal, stalactitic, and other imitative shapes : surface 

 generally rough, sometimes also smooth, composition im- 

 palpable, fracture flat conchoidal. Massive : composition 

 granular, of various sizes of individuals, often impalpable, 

 and strongly coherent, fracture uneven or flat conchoidal. 



1. Upon charcoal, it becomes black before the blow-pipe, and red on 

 cooling. It melts into a globule, which becomes magnetic if kept in the 

 blast for some time. With borax, it yields a globule of copper. It is 

 partly soluble in dilute nitric acid; the solution is green, and the undis- 

 solved part consists of sulphur. 



2. Analysis. 

 By ROSE. 



Sulphur 35-37 



Iron 29-82 



Copper 34-81 



3. It is found in veins and beds. In the latter, it is attended by vari- 

 ous ores of iron and copper, by Galena, Blende, &c. In veins by a great 

 variety of species among which several ores of silver frequently occur. 



4. It occurs in numerous countries; but the finest crystals come from 

 Freiberg and Cornwall. It occurs in the United States at several 

 places; at the Southampton (Mass.) lead-mine with Galena and Blende, 

 at Franconia, (N. H.) in gneiss, at Stratford and Schrewsbury, (Vt.) 

 with Magnetic Iron Pyrites, &c. 



5. It is a very valuable ore for the production of copper. 



YELLOW LEAD-ORE. Pyramidal Lead-Ba- 



ry t e. MOHS. 



Primary form. Octahedron with a square base. P on 

 P"=130 II 7 . 



