9 S A SYSTEM OF 



Is diftinguifned from the martial glim- 

 mer, or mica, (Seel, xcv.) by the icales 

 bein^ lefs mining, thicker, and rectan- 

 gular. 

 a. Black. This, when rubbed fine, gives a 



green powder. 

 h. Greenifh- 



Both thefe, particularly the black, are 



found every where in Sweden among the 



iron ores, and in the Grunften (Section 



eclxix *). 



SECT. LXXXIX. 



ZX Tripoli, tferra 'Tripolitana. 



Is known by its quality of rubbing hard 

 bodies, and making their furfaces to mine, 

 the particles of the tripoli being fo fine, as 

 to leave even no fcratches on the furface. 

 This effect, which is callepl polifhing, may 

 likewife be effected by other fine clays, when 

 they have been burnt a little. The tripoli 

 grows fomewhat harder in the fire, and is very 

 refractory : it is with difficulty diffolved by 

 borax, and ftill with greater difficulty by the 

 microcofmic fait : it becomes white when it is 

 heated : when crude, it imbibes water, but 

 is not diffufible in it : it taftes l«ke common 

 chalk, and is rough or fandy between the 

 teeth, although no fand can by any means be 

 feparated from it. It has no quality common 



* The hornblende grows hard in the fire, which is the rea- 

 fon why it is ranked here among the clays, though in all its 

 other qualities it much refembles the cockle or fhirl. (Section 

 lxxii.) E. 



with 



