ORDER r. PRISMATIC TALC-MICA. 1Q3 



Carbon 81-00 92-00 9C-00. 



Iron 10-00 8-00 4-00. 



Oxygen 9-00. SCHEELE. 0-00. VAUQ. 0-00. SAUSS. 

 In a high degree of heat it is combustible, and leaves a 

 residue of oxide of iron. It is infusible alone, and with 

 additions. 



3. The varieties of this species are found in beds, or 

 form beds by themselves, in slaty and ancient trap-rocks. 

 They seem often to replace the different species of 

 Talc-mica in mixed rocks, particularly in gneiss, if con- 

 taining a great proportion of Feld-spar. In the beds of 

 rhombohedral Lime-baloide, the rhombohedral Graphite- 

 mica occurs in single crystals, or in imbedded massive varie- 

 ties. It is likewise met with in the coal formation. 



4. One of the most remarkable repositories of rhombo- 

 hedral Graphite-mica is at Borrowdale in Cumberland, a 

 bed of trap very much interrupted, and alternating with 

 clay-slate. In the neighbourhood of Hafnerzell, Gries- 

 bach, &c. in Passau, in Austria, Moravia, and other coun- 

 tries, it forms a constituent part of gneiss ; in Lower Stiria 

 it is imbedded in granular limestone. It occurs crystallis- 

 ed in Greenland, in the parish of Pargas in Finland, and 

 different varieties are known from the Tyrol, Salzburg, 

 Piedmont, France, Spain, Norway, and America. In the 

 coal formation it is found at Cumnock in Ayrshire. 



5. The chief employment of this mineral is in manufac- 

 turing pencils and crucibles, the latter particularly for the 

 purposes of the mint. It is also used for giving a gloss to 

 iron stoves and railings, and for diminishing the friction 

 in machines. 



GEXUS V. TALC-MICA. 

 1. PAISMATIC TALC-MICA. 



Rhomboidal Mica (in part). JAM. Syst. Vol. II. p. 

 221. Prismatic Talc-Mica (in part). Man. p. 119. 

 Talc. Green Earth. Chlorite. PHILL p. lie. liy. 120. 



YOL II. N 



