286 DESCRIPTIONS OF MINERALS. 
Cyanite.—Kyanite. Disthene. 
Trislinic. 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 hght 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. 5-15 d, greatest 
at the ends of the prisms, and least on the flat face of the 
piisme @ Gs =a 40-3" 7% 
Composition. A1O,Si, as for andalusite,=Silica 36°9, 
alumina 63°1=100. Blowpipe characters like those of an- 
dalusite. 
Diff. Distinguished by its infusibility from varieties of 
the hornblende family. ‘Lhe short crystals have some re- 
semblance to staurolite, 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. 
Obs. Found in gneiss and mica schist, and often accom- 
panied by garnet and staurolite. 
Occurs in long-bladed crystallizations at Chesterfield and 
Worthington, Mass. ; ab Litchfield and Washington, Conn. ; 
near Philadelphia; near Wilmington, Delaware; and in 
Buckingham and Spotsylvania counties, Va. Short crystals 
(sometimes ealled improperly fidrolite) 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 kuanos, a dark-blue 
substance. It is also-called disthene, in allusion to the un- 
equal hardness in different directions, and when white, rhe- 
tizite. . 
Kyanite is sometimes used as a gem, and has some resem- 
blance to sapphire. 
Topaz. 
Trimetric. IA 7=124° 17’. Rhombic prisms, usually dif- 
ferently modified at the two extremities. JAJ= 123° ae 
Cleavage perfect parallel to the base. 
Color pule yellow ; sometimes white, greenish, bluish, or 
Pa 
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