in the interior of Cupriferous Minerals. 129 



description of I'^T 19' situated like the one of 122° ; but the 

 prism being supposed to be a right rhombic one, it follows that 

 the other two angles will be 115° 22' and 122° 19'. Besides, 

 Haiiy gives a specific gravity of 2.733 to his crystals, while 

 the varieties of chrysocolla never go beyond 2.2. I know 

 only one specimen, with crystals apparently homogeneous, and 

 resembling chrysocolla, engaged in a pale brown clayey sub- 

 stance. It forms part of the magnificent collection of Mr 

 Bergemann of Berlin, who intended to subject it to a chemi- 

 cal analysis, while Professor Gustavus Rose was to examine 

 its mineralogical, and particularly its crystallographic charac- 

 ters. We have therefore to look to the ability and zeal of the 

 Berlin mineralogists and chemists for more accurate informa- 

 tion regarding this remarkable substance. 



The blue copper, ground to an impalpable powder, is em- 

 ployed as a blue paint, of a very bright tint, paler than the 

 mineral itself. It is not, however, highly valued, because it 

 is apt to lose its original colour, and to turn green. This is 

 mentioned by Haiiy, who quotes authorities as old as Walle- 

 rius, and even Boetius de Boot, for the colour of the Arme- 

 nian stone of the ancients. * The decomposition of the blue 

 pigment is a case exactly similar to that of the blue crystals, 

 as presented by the specimens found in mines. 



Copper in its metallic state, when exposed to the action 

 of the atmosphere, variously combines with the elements con- 

 tained in that fluid. -[■ I have seen remains of Egyptian ves- 

 sels, in the possession of Captain T. D. Stewart, which had ,^^; 

 formerly consisted of copper or bronze, and still presented the w 

 (exact outline of their original shape, with a pretty smooth sur- 

 face. Some of the fragments were nearly one-fourth of an 

 inch thick ; but so complete was their disintegration, that they 

 could be easily broken across with the hands, presenting on 

 their fracture a compound mass full of small drusy cavities. 

 In these the octahedral crystals of the copper ore, of which 

 the whole mass consisted, were distinctly visible. The curved 

 surface of most of the vessels was covered with atacamite, 



* Traite de Min. 2de Edit. t. iii. p. 503 



t This fact is mentioned in the translation of Mohs' Treatise on Mine' 

 raiogy, vol. ii. p. 383. 



VOL. VII. NO. I. JULY 1827- i' WjAq^^dfei'^i 



