28G DESCRIPTIONS OF MINERALS. 



Cyanite. — Kyanite. Disthene. 



Tri clinic. Usually in long thin-bladed crystals aggre- 

 gated together, or penetrating the gangue. Sometimes in 

 short and stout crystals. Lateral cleavage distinct. Some- 

 times fine fibrous. 



Color usually light blue, sometimes having a blue centre 

 with a white margin; sometimes white, gray, green, or even 

 black. Lustre of flat face a little pearly. H. =5-7*5, greatest 

 at the ends of the prisms, and least on the flat face of the 

 prism. G-. =3'±5-o'7. 



Composition. A10 5 Si, as for andalusite, = Silica 36'9, 

 alumina 63 '1 = 100. Blowpipe characters like those of an- 

 dalusite. 



Biff. Distinguished by its infusibility from varieties of 

 the hornblende family. The short crystals have some re- 

 semblance tostaurolite, but their sides and terminations are 

 usually irregular ; they differ also in their cleavage and 

 lustre. The thin-bladed habit of cyanite is very character- 

 istic. 



Oos. Found in gneiss and mica schist, and often accom- 

 panied by garnet and staurolite. 



Occurs in long-bladed crystallizations at Chesterfield and 

 Worthington, Mass. ; at Litchfield and Washington, Conn. ; 

 near Philadelphia ; near Wilmington, Delaware ; and in 

 Buckingham and Spotsylvania counties, Va. Short crystals 

 (sometimes called improperly fibrolite) occur in gneiss at 

 Bellows Falls, Vt., and at Westfield and Lancaster, Mass. 



In Europe, at St. Gothard in Switzerland, at Greiner and 

 Pfitsch in the Tyrol, in Styria, Carinthia, and Bohemia. 

 Villa Rica in South America affords fine specimens. 



The name cyanite is from the Greek huanos, a dark-blue 

 substance. It is also called disthene, in allusion to the un- 

 equal hardness in different directions, and when white, rhce- 

 tizite. 



Kyanite is sometimes used as a gem, and has some resem- 

 blance to sapphire. 



Topaz. 



Trimetric. 7a I— 124° 17'. Rhombic prisms, usuallv dif- 

 ferently modified at the two extremities. IM- 124° 17'. 

 Cleavage perfect parallel to the base. 



Color pale yellow ; sometimes white, greenish, bluish, or 



