196 



PHYSIOGRAPHY. 



Fahlunite Feldspar. 



2. Analysis. 

 By TROLLE-WACHTMEISTER. 



A black m 

 Sp. 



Silica 

 Alumina 

 Oxide of iron 

 Magnesia 



Protoxide of manganese 

 do. mixed with ox. of iron 

 Soda 

 Potash 



Fluoric acid with silica 

 Lime 

 Water 



3. It occurs at Fahlun in Sweden, in a talcose or chloritic slate, with 

 Galena and Copper Pyrites. 



FASSAITE. (See Pyroxene.} 

 FELDSPAR. Orthotomous Feld-spar. MOHS. 



Primary form. Doubly oblique prism. * M on T = 

 120. PonM=90. P on T =67 15', 



Fig. 182. 



* In the description of this species, it has been found the most conven- 

 ient to represent the crystals after the method of HATJY, in preference 

 to that of BROOKE, whose projections have generally been adopted in 

 (he present work. 



