TAB. CCXII. 
Tis pretty specimen was sent from the same place as the 
last, and is of rather an unusual colour and appearance ; 
having additional bevillings and truncations; viz. two on 
each of the more obtuse edges of the prism, forming four 
_ additional faces, and making in all ten faces to the prism 
and two small faces on the apex. | 
Feldspar differs in specific gravity from 2°272 to 2°7045. 
Under the blowpipe it melts into a whitish glass without 
addition. It also varies in analysis, containing 
Silex: trom .)7. «42 4to7@ 
Alumine . . : 14 — 37 
Lime, sometimes Oxide of Iron, and also Potash ; 
Barytes and Magnesia, according to Mr. Kirwan. 
TAB. CCXITI, 
Pernars one of the most curious circumstances which ~ 
happens in this substance, is that of its crystals macling, 
which in this specimen they most truly do, according to 
the literal sense of that word, as distinguished from the 
hemitrope*. The present specimen is of a peculiar kind, 
* A crystal one half of which is turned upon the other.—Haizy, 
