530 REPORT OF NATIONAL MUSEUM, 1900. 



]Minsis Geraes, Brazil, where it occurs rather abundantly in crystals 

 closeh' reseniblino- chrvsober3'l in color. 



Spodumcno contains in 100 parts: Silica, 6-1.5; alumina, 29.3; 

 lithia, 6.2. 



STAUROLITE. 



FAIRY STONE. 



Staurolite is occasional!}' used as a gem. It occurs in orthorhombic 

 crystals of a prismatic habit, often cruciform from twinnino-. Color, 

 dark reddish brown to brownish black. Hardness, 7.5; specific grav- 

 ity, 3.T. The transparent kinds when cut resemble garnets. From 

 their resemblance to a cross, the twinned forms are used to quite an 

 extent as ornaments and charms, a use based to a certain degree upon 

 the belief that they fell from heaven. Staurolite occurs commonly 

 embedded in schist and gneiss. 



One hundred parts contain: Silica, 29.3; alumina, 53.5; peroxide 

 of iron, 17.2.. 



THOMSONITE. 



LIXTOXITE. 



The thomsonite, and a variety, lintonite, occurring as amygdules in 

 the basalt and as rolled pebbles on the beaches of Lake Superior, tind 

 a limited use as gem minerals. The pebbles vary in size from that of 

 a pea to a hickory nut, and are often made up of a series of concentric 

 layers of various shades of color, flesh red and other reds, green, 

 yellow, and white; affording, when polished, an attractive ornament 

 resembling the eye agate. Hardness, 5.5; specific gravity, 2 A; luster, 

 vitreous, inclining to pearly. 



One hundred parts contain: Silica, 37.4; alumina, 31.8; lime, 13; 

 soda, 4.8; water, 13. 



TITANITE. 



Titanite, or sphene, is employed to some extent as a gem mineral. 

 Its hardness is 5.5; specific gravity, 3.5; luster, vitreous; color, brown, 

 gray, yellow, green, and black; possessing strong refractive and dis- 

 persive powers on light. The transparent and colorless, greenish or 

 yellowish kinds when cut show a great deal of fire and present an ap- 

 pearance approaching that of the fire opal. 



One hundred parts contain: Silica, 30.45; titanic oxide, 41.33; lime, 

 28.22. 



TOPAZ. 



Topaz crystallizes in the orthorhombic system, occurring commonly 

 in prismatic forms having the prism faces more or less striated verti- 

 cally; also occurring massive. The mineral has a highly perfect basal 

 cleavage, i. e., transverse to the length of the prism; a hardness of 8; 



