MINERALOGY. 431 



Pyrope, or Bohemian garnet, is the most abundant vari- 

 ety. Found in Bohemia, embedded in trap tufa, gneiss, 

 and granite; occurs generally in rounded or angular 

 grains ; are very beautiful and bring a high price. 



II. Schorl Tourmaline is of vitreous luster, and 

 occurs as compact, massive, and coarse columnar crystals, 

 transparent ; usually translucent to opaque ; color white, 

 yellow, brown, red, green, or black ; hues not brilliant, 

 except the varieties of red and green. The electric pol- 

 arity of the fractured crystals, when heated, is a remark- 

 able characteristic of this mineral. Fracture conchoidal, 

 passing into uneven ; brittle. H. = 7.0, to 7.5 ; G. = 

 3, 0, to 3, 3. The most important of this family is 



The Common Tourmaline, which occurs as a compact 

 crystal-like structure ; sometimes columnar, fine, slender, 

 a*hd stem-like ; found usually in granite, gneiss, and mica 

 slate, in various localities ; in Europe abundantly, on the 

 St. Gothard. Color mostly the same with that of the 

 above described, except that it is never red ; some varie- 

 ties are black. Tourmalines, by burning, generally in- 

 tumesce more or less ; some, those containing lime, fusing 

 readily ; others assuming a slaggy appearance, are of 

 very difficult fusibility. A relative variety, very trans- 

 parent, green or red, which never melts, but successfully 

 resists the action of fire, is called Aphrite, and was 

 most probably the Hyacinth of ancient times. 



III. Zeolite. H. = 5.0, to 5.5 ; G. = 2.1 to 2.25. 

 Luster vitreous ; color yellow, red, or yellowish light 

 gray. The best representative of this family is 



Natrolite, a beautiful stone or gem, which receives its 

 name from natron, soda. Found in basalt and volcanic 

 rocks ; shape prismatic, usually slender ; also in globular, 

 stellated groups, on a white or green ground. Luster 



