104 A SYSTEM Of 



Thefe are known by the following cha- 

 racters. 



i. Their texture and compofition confift of 

 thin flexible particles, divifible into plates 1 

 or leaves, having a- mining furface. 



2. Thefe leaves, or fcales, expofed to the 

 fire, lofe their flexibility, and become 

 brittle, and then feparate into thinner 

 leaves : but in a quick and ftrong fire, 

 they curl or crumple, which is a mark of 

 fufion j though it is very difficult to reduce 

 them into a pure glafs by thernfelves, or 

 without addition. 



3. They melt pretty eafily with borax, the 

 microcofmic fait, and the alcaline fait •, and 

 may, by means of the blow-pipe, be 

 brought to- a clear glafs, with the two 

 former falts. The martial mica is, how- 

 ever, more fufible than the uncoloured 

 ones. 



There is not yet difcovered any loofe 

 earth of this kind, but it is always feund 

 indurated. 



SECT. XCIV. 



A. Colourlefs or pure mica ; Daze, Glimmer, 

 or Glifl ; Mica alba, five pur a* 



1. Of large parallel plates, Mica conftans 

 lamellis magnis paralklis. Mufcovy glafs, 

 Vitrum Mufcoviticum. 



Is tranfpajent as glafs •, found in Siberia, 

 and Elfdalen in the province of Wer- 

 meland. 



2. Of fmall plates, Mica fquamofa, from Silf- 

 verberget, at Runneby, in the province 

 of Blekinge. 



*. Of 



