320 PHYSIOGRAPHY. CLASS n. 



the direction of the axis, yellowish-grey perpen- 

 dicular to it. 



Hardness = 7-0 ... 7-5. Sp. Gr. - 2-583, of a 

 transparent variety. 



Compound Varieties. Massive : composition 

 granular, strongly connected, and difficultly re- 

 cognised. 



OBSERVATIONS. 



1. If in the two species formerly distinguished among 

 the varieties of prismatic Quartz, we pay no attention to 

 their mode of occurrence and localities, no characters, how- 

 ever accidental, remain, hy which they might be distin- 

 guished. SteinhelUte and Hard Fahlunite likewise belong to 

 the present species, and seem to contain varieties which 

 will allow us some day to establish their forms with a great- 

 er degree of precision. 



2. According to STROMEYER, the present species con- 

 sists of 



Silica 48-538. 



Alumina 31730. 



Magnesia 1 1 -305. 



Oxide of Iron 5-68G. 



Oxide of Manganese 0-702. 



Water or Loss 1-648. 



Before the blowpipe it melts in a good heat, but with dif- 

 ficulty, and only on its edges, into a glass not inferior to 

 the mineral, either in colour or transparency. 



3. Prismatic Quartz occurs in aggregated crystals, with 

 dodecahedral Garnet, rhombohedral Quartz, &c. at Cabo 

 de Gata in Spain, in the bay of San Pedro, and these va- 

 rieties have been called lolitc. Peliom occurs at Boden- 

 mais in Bavaria, sometimes in very distinct crystals, but 

 generally massive, with rhombohedral Iron-pyrites, &c. 

 Other varieties have been found imbedded in various kinds 



