132 



SILICA. 



tumesces before the blowpipe without fusing. Occurs in veins in clay 

 slate at Salzberg and inStyria; in the United States, near Crowdei 

 Mountain, Lincoln county, N. C. 



Mellite or Honey stone. In square octahedrons, looking like a honey- 

 yellow resin ; may be cut with a knife. It is mellate of alumine 

 Found in Prussia and Austria. 



Cryolite. In snow white masses, having rectangular cleavages, and 

 remarkable for melting easily in the flame of a candle, to which its 

 name (from the Greek kruos, ice,) alludes. H=225 — 2 5. Gr=2 - 95. 

 It is a fluorid of aluminium and sodium. From Greenland. 



Chiolite is near cryolite in composition and characters. H=3'5. 

 Gr=2-6— 290. From Siberia. 



Fluellite. From Cornwall, in minute white rhombic octahedrons. 

 Contains fluorine and aluminium. 



Childrenite. Found in Derbyshire, Eng., in minute yellowish brown 

 crystals coating spathic iron. Consists of phosphoric acid, alumina and 

 iron, with water. 



Amblygonile. A compound of phosphoric acid, alumina and lithia. 

 Found in Saxony, in pale green crystals. 



Diaspore, or Dihydrate of Alumina. Occurs in irregular lamellai 

 prisms, having a brilliant cleavage ; color greenish gray or hair brown. 

 H=6— 7-0. Gr=343. It decrepitates with violence before the blow- 

 pipe. From the Urals, in granular limestone. At Trumbull, Ct. 



CLASS VI.— EARTHY MINERALS. 



1. SILICA. 



QUARTZ. 



^ 



^y^Lj 



Rhombohedral. Occurs usually in six-sided prisms, more 

 or less modified, terminated with six-sided pyramids : R ; R= 

 94° 15'. No cleavage apparent, seldom even in traces ; but 

 sometimes obtained by heating the crystal and plunging it 

 into cold water. The following are some of its forms : 

 12 3 4 5 



Oi 



Occurs sometimes in coarse radiated forms ; also coarse 

 and fine granular ; also compact, either amorphous or pre. 

 senting stalactitic and mamillary shapes. 



Crystals are often as pellucid as glass, and usually color 



What is the usual form of quartz crystals? 



