360 PHYSIOGRAPHY. CLASS u. 



edges of combination with the hexahedron. The 

 surface of the grains is uneven, rarely granulated. 

 Lustre vitreous, inclining to resinous in some va- 

 rieties, more nearly the latter. Colour red, brown, 

 yellow, white, green, black ; except some red co- 

 lours, none of them are bright. Streak white. 

 Transparent ... translucent. 



Hardness = 6-5 ... 7-5. Sp. Gr. rr 3-615, Gros- 

 sular; 3-701, Melanite ; 3-769, brown, common 

 Garnet ; 3-788, Pyrope ; 4 098, crystals of pre- 

 cious Garnet, Tyrol ; 4-125 grains of precious 

 Garnet, Ohlapian ; 4-179, crystals of Almandine ; 

 4-208, crystals of precious Garnet, Haddam. 

 Compound Varieties. Massive: composition gra- 

 nular, of various sizes of individuals, and often even 

 impalpable, easily separated or strongly coherent ; 

 faces of composition irregularly streaked, uneven 

 or rough. If the composition be impalpable, the 

 fracture becomes uneven and splintery. The com- 

 position is sometimes thick lamellar, and bent, the 

 faces of composition being pretty smooth. 



OBSERVATIONS. 



1. The numerous and manifold varieties of those mine- 

 rals which are at present united within the species of 

 dodecahedral Garnet, present such properties as render 

 it likely, that they will be at some future period distin- 

 guished into several really distinct species. Particularly 

 the limits of hardness and of specific gravity are more 

 distant than we are accustomed to find it in one and the 

 same species. Those inquiries, however, which have been 

 hitherto instituted into their natural-historical properties, 

 are not sufficient to establish clear and constant limits, and in 



