127 



the accumulation on the sides, forming the hexaedral plates. 

 The right hand geometrical figure shows the rectangular 

 primitive or cubic form within the column, which by a little 

 thought may by a tyro be comprehended as the primitive 

 form that accumulates to that of the left hand figure. The 

 hexangular column has four angles of 121° and two of 1 ] 8°. 

 The gangue is composed of Chlorite, Quartz, Oxide of 

 Tin, and Arsenical Iron, or Mispickel. The specimen 

 comes from Cornwall. 



Tungstate of Iron has not, that I know of, been found 

 Otherwise than crystallized, although the crystals are almost 

 always interrupted. It may be known from most other 

 substances by its peculiar fracture, which in the tabular 

 crystals is perpendicular to their larger faces. It may be 

 scraped by a knife, giving a chocolate brown powder. 



