ORDER IX. OCTAHEDEAL COPPER. 445 



Lustre metallic. Colour copper-red. Streak un- 

 changed, shining. 



Ductile. Hardness = 2-5 ... 3-0. Sp. Gr. = 

 8-5844, HAUY. 



Compound Varieties. Twin-crystals very fre- 

 quent, composed parallel to a face of the octahe- 

 dron. If the form of the individuals is the icosite- 

 trahedron A 2, and the compound crystal flattened 

 in the direction of the axis of revolution, isosceles 

 six-sided pyramids are formed, which at first sight 

 appear not to belong to the tessular system. Small 

 crystals aggregated in rows ; arborescent and fili- 

 form shapes. Massive: composition not recognis- 

 able. Plates, often consisting of distinct crystals. 

 Superficial. 



OBSERVATIONS. 



1. The octahedral Copper is the pure metal as produced 

 by nature. Before the blowpipe it melts pretty easily, but 

 is covered on cooling with an oxidised coat. It is easily 

 soluble in nitric acid, and yields under the influence of light 

 and air, a blue solution in ammonia. It crystallises from 

 fusion ; crystals, dentiform and capillary shapes, are often 

 produced in the vesicular cavities of copper-slags. 



2. It is found in beds and veins, and is associated with 

 various other ores of copper, sometimes with ores of iron, &c. 



3. Among the metals, hexahedral Copper is one of those 

 which are not uncommonly found in the native state ; and 

 even in our times examples have occurred of large masses 

 that have been met with in several countries. In beds it 

 occurs at Herrengrund, Schmolnitz, and Gollnitz ; also at 

 Moldawa, Saska, and Orawitza, in the Bannat of Temes- 

 war ; probably in the same manner in Siberia, from whence 

 the largest and most distinct crystals of the general shape 

 of the hexahedron have been brought, for the greater part 



