156 



Outlines of the Mineralogy and Geology 



It is easily frangible. 



The fragments are tabular, approacliing to rhomboidal^ or in 

 determinately angular and sliarp edged. 



Its specifick gravity is from about S.60 to S.655. 



Chymical Character, 

 Before the blowpipe it fuses into a whitish ^lass or enamel. 



Geological Situation and Localities, 



1 B 



J 



Feldspar is a component part of the rocks in this vicinity, as 

 Sienite, Greenstone, Porphyry, and Grauite. At Carlisle, a beau- 

 tiful cream coloured variety is fouud, which is eas 



9 



is easily frangible 

 and the fragments are rhomboidal. The reddish varieties are 

 found chiefly at Burlington and Wilmington, in Granite. At 



r 



Charlestown a curious variety is found in a bed of Sienite in Green- 

 stone. The mass is a union of singular crystals, which are either 

 parallelopipedons or tables ; they have generally a white nucleus 

 surrounded by lamina of a red or green 

 fectly well defined and distinct from 



colour, which 



per 



the 



the latter 



disappears, and the cavity is studded either with crys 



tals of Epidote or Quartz, or it is filled with Hornblend 



The 



blackish var 



Charlestown 



ty 



found imbedded 



Greenstone porphyry 



