100 PHYSIOGRAPHY. 



Petalite. 



PEHITOMOUS LEAD-BARYTE. (See Kerasite.) 

 PETALITE. Prismatic Petaline-Spar. MOHS. 



Primary form. Doubly oblique prism ? 



Cleavage, a prism of 95 nearly, and parallel with its 

 longer diagonal ; the latter more distinct. Fracture imper- 

 fectly conchoid al. 



Lustre vitreous, inclining to resinous ; pearly upon faces 

 of cleavage. Color white, with tinges of blue, pink and 

 green. Streak white. Translucent. 



Britile. Hardness =6-0 . . . 6*5. Sp. gr. =2-439. 



Compound Varieties. Massive ; composition colum- 

 nar, of various sizes of individuals, sometimes impalpable, 

 and generally strongly coherent. If the composition be 

 impalpable, the fracture is splintery. Extremely tough. 



1. If exposed to the highest heat of the blow-pipe on charcoal, it be- 

 comes glassy, semi-transparent and white, but melts only upon the edges. 

 If gently heated, it emits a blue, phosphorescent light. 



2. Analysis. 



By ARFWEDSOX. By GMELIN. 



Silica . . 79-212 . . . 74-17 



Alumina . . 17-225 . . . 1741 



Lithia . . 5761 . . . 5-16 



Lime . . 0-000 . . . 0-32 



3. Petaiite occurs in the Swedish island of Uton, where it occurs in 

 boulders of limestone, accompanied by Quartz, Feldspar and Tourmaline. 

 In the United States, its only locality is Bclton, (Mass.) where it existi 

 in a lime-quarry, along with Scapolite, Sphene and Pyroxene. 



PETROLEUM. (See Bitumen.) 

 PETROSILEX. 



Massive : composition impalpable. Fracture fine grained. 

 Lustre waxy. Colors various, grey, green, brown and red. 

 Translucent. 

 Hardness = 7-0. 



