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rpars, mica, and fhoerls, are very confpicu- 

 ous to the eye. The ilioerls are rhomboidal 

 prifms, a line, or two lines, in length, at 

 the moft, and about half as broad, femi- 

 tranfparent, of a whitifh colour, fhining 

 but little on the furface, but very confidera- 

 bly in the fractures, and with a luflire of 

 changeable colours. The mica is, for the 

 moil part, black ; but fometimes of a 

 golden yellow, and in flat, hexaedral, 

 opake, laminous, and extremely lucid 

 • prifms, the largeft of which are little more 

 than a line in length. Thefe two ftones 

 are rather numerous ; but the fhoerls, which 

 are, for the moft part, lir.ear, are but few. 

 They are all three contained in a petrofili- 

 ceous pafte, become earthy by decompo- 

 fition, and, at the furface of the prifmatic 

 columns, almoft pulverulent, and of the co- 

 lour of a dead leaf; but internally it pre- 

 ferves the cbarader of the petrofilex, giving 

 fparks more or lefs with fleel, and being of 

 a dark colour. The furnace converts thefe 

 columns into an enamel inclining to a black 



colour. 



