ORDER ix. HEXAHEDRAL GOLD. 437 



burg, Siberia ; As, Vol. I. Fig. 32., Siberia ; 

 Cfi (o) Vol. I. Fig. 34., Transylvania. 



Char, .of Comb. Tessular. 



Combinations. 1. H. O. Vol. I. Fig. 3. and 4., 

 Matto Grosso, Brazil. 2. H. D. Fig. 151. 

 3. H. C*. Fig. 153. 4. H. O. C*. The three 

 last from Transylvania. 



Cleavage, none. Fracture hackly. Surface ; the 

 hexahedron often hollow ; the octahedrons either 

 rough or smooth, in combinations generally the 

 latter ; the icositetrahedrons streaked parallel to 

 the edges of combination with the hexahedron 

 and the octahedron. These differences in most 

 cases are not distinctly marked. 



Lustre metallic. Colour, various shades of gold- 

 yellow. Streak shining. 



Ductile. Hardness 2-5... 3-0. Sp. Gr. = 14-857, 

 a rolled mass of a high gold-yellow colour; 

 = 19-2527, melted, HAUY. 



Compound Varieties. Twin-crystals: face of 

 composition parallel, axis of revolution perpendicu- 

 lar to a face of the octahedron ; pretty frequent, 

 particularly in the icositetrahedrons, as represented 

 in Fig. 157. If this variety be compressed in the 

 direction of the axis of revolution, Fig. 178 is 

 formed, having the appearance of an isosceles six- 

 sided pyramid combined with a three-sided one, 

 similar to the crystals, which are described in the 

 Catalogue of the Collection of Mr VON DER NULL, 

 Part III. p. 42., but without mentioning the regu- 



