268 



DESCRIPTIONS OF MINERALS. 



A green variety occurs at Unity. Maine, near Baltimore, 

 Md.. and at Chestnut Hill, Pa. Prismatic mica is found at 

 Russel, Mass. 



On account of the toughness, transparency, and the thin- 

 ness of its folia, mica was formerly used in Siberia for glass in 

 windows, whence it has been called Muscovy glass. It is in 

 common use for lanterns, and also for the doors of stoves, 

 and other purposes which demand a transparent substance 

 not affected by heat. 



Lepidolite, or Litliia mica. Resembles niuscovite. Color rose-red, 

 and lilac to white ; in crystalline plates and aggregations of scales. 

 It contains from 2 to 5 per cent, of litliia, and hence B.B. imparts a 

 deep crimson color to the flame. 



From Rozena in Moravia ; Zinnwald in Bohemia (the Zinmcaldite) ; 

 Saxony: the Ural; Sweden; Cornwall; Paris, and Hebron, Maine ; 

 Chesterfield, Mass. ; Middletown, Conn. The red mica of Goshen is 

 muscovite. 



OryophyUUe has the same constituents as lepidolite. It fuses easily 

 in the name of a candle. From Cape Ann, Mass. 



Dimetric. 1 



SCAPOLITE GROUP. 



The Scapolite species are dimetric in crystallization, 

 usually white in color or of some light shade, and analyses 

 afford alumina and lime with or without soda. The lime 

 scapolites are unisilicate in ratio ; the others, containing 

 alkali, have, with one exception, more silica than this ratio 

 requires. 



Wernerite. — Scapolite 



1 = 136° ?". Cleavage rather indistinct paral- 

 lel with i-i and I. Also massive, sub- 

 lamellar, or sometimes faintly fibrous 

 in appearance. 



Colors light : white, gray, pale blue, 

 greenish or reddish. Streak uncolored. 

 Transparent to nearly opaque. Lustre 

 usually a little pearly. H. =5-6. G. = 

 2-6-2-8. 



Composition. (-J(Ca,Xa»)f A1) 9 12 Si 3 = 



Silica 48-4, alumina 28*5, lime 18*1, 



soda 5*0=100. B.B. fuses easily with intumescence to a 



white glass. Imperfectly decomposed by hydrochloric acid. 



