ORES OF TITANIUM. 



211 



This ore is employed in painting on porcelain, and quite 

 largely for giving the requisite shade of color and enamel 

 appearance to artificial teeth. 



Anatase. Brookite. These species have the same composition aa 

 rutile. Anatase occurs in slender nearly transparent octahedrons, of a 

 brown color. A : A=97° 56'. H=55— 6. Gr=38— 39. From 

 Dauphiny, the Tyrol, and Brazil. Said to accompany native titanium 

 in slags from the iron furnaces of Orange county, N. Y. 



Brookite is met with in thin hair-brown crystals, attached by one 

 edge. H=5"5 — 6. The crystals are secondaries to a rhombic prism. 

 From Dauphiny, and Snowdon in Wales. Said to occur at the Phenix- 

 ville tunnel on the Reading railroad, Pa. Arkansite is Brookite. 



SPHENE. 



Monoclinic. In very oblique rhombic prisms ; the lat- 

 eral faces having angles either of 76° 1', 113' 28' (r : r) 

 1 2 3 



136° 4' (n : n), or 133' 48'. The crystals are usually thin 

 with sharp edges. Cleavage in one direction sometimes 

 perfect. Occasionally massive. 



Color grayish-brown, gray, brown or black ; sometimes 

 yellow or green ; streak uncolored. Luster adamantine to 

 resinous. Transparent to opaque. H = 5 — 5.5. Gr= 

 3*2—3-6. 



Composition: silica 30*5, titanic acid 41*3, lime 28*2. 

 Before the blowpipe, the yellow varieties are unaltered in 

 color, and others become yellow ; on charcoal, they fuse on 

 the edges with a slight intumescence to a dark glass. 



The dark varieties of this species were formerly called 

 'itanite, and the lighter sphene. The name sphene alludes 

 o the wedge-shaped crystals, and is from the Greek sphcn, 



wedge. 



What is said of the crystals of sphene 1 What are .he color, lusttr, 

 and hardness 1 the composition f 



