64 



PHYSIOGRAPHY. 



Native Copper. 



5. Fig. 320. 



Siberia. 



Nalsoe. 



Cleavage, none. Fracture hackly. Surface generally 

 not very smooth, but nearly of the same quality in all the 

 forms, excepting the dodecahedron, which is sometimes 

 streaked parallel to its edges of combination with the cube. 

 It is subject to tarnish. 



Lustre metallic. Color copper-red. Streak unchanged, 

 shining. 



Ductile. Hardness =2-5 . . . 3-0. Sp. gr. = 8'5844. 



Compound Varieties. Twin-crystals very frequent, 

 composed parallel to a face of the octahedron. If the 

 form of the individuals is the icositetrahedron, and the com- 

 pound crystal flattened in the direction of the axis of revo- 

 lution, isosceles six-sided pyramids are formed, which at 

 first sight appear incapable of derivation from the cube. 

 Small crystals aggregated in rows ; arborescent and fili- 

 form shapes. Massive : composition not recognizable. 

 Plates, often consisting of distinct crystals. Superficial. 



1. Before the blow-pipet it melts pretty easily, but on cooling is cov- 

 ered with an oxidized coat. It is easily soluble in nitric acid, and yields 

 under the influence of light and air, a blue solution in ammonia. It 

 crystallizes from fusion. Dentiform and capillary crystals are often pro- 

 duced in the vesicular cavities of copper slags. 



