308 REPORT OF NATIONAL MUSEUM, 1899. 



are used mainly for abrading purposes and mainly as a sand for sawing 

 and grinding stone or for making sandpaper. .The material is of less 

 value than corundum or emery, owing to its inferior hardness. The 

 commercial value is variable, but as prepared for market it is worth 

 about 2 cents a pound. 



5. ZIRCON. 



This is a silicate of zirconium, ZrSiO 4 , = silica 32.8 per cent; zirconia 

 67.2 per cent; specific gravity 4.68 to 4.7; hardness 7.5; colorless, gray- 

 ish, pale yellow to brown or reddish brown. Ordinarily in the form 

 of square prisms. Specimens Nos. 61133 and 62581, U.S.N.M., are 

 characteristic. 



Zircon is a common constituent of the older eruptives like granite 

 and syenite, and also occurs in granular limestone, gneiss, and the 

 schists. It is so abundant in the elseolite syenites of southern Norway 

 as to have given rise to the varietal name Zircon syenite. Although 

 widespread as a rock constituent it has been reported in but few 

 instances in sufficient abundance to make it of commercial value. 

 Being hard and very durable it resists to the last ordinary atmospheric 

 agencies, and hence is to be found in beds of sand, gravel, and other 

 debris resulting from the decomposition of rocks in which it primarily 

 occurs. It has thus been reported as found in the alluvial sands in 

 Ceylon, in the gold sands of the Ural Mountains, Australia, and other 

 places. In the United States it occurs in considerable abundance in 

 the elseolite syenite of Litchfield, Maine, and is also found in other 

 States bordering along the Appalachian Mountains. The most noted 

 localities are in Henderson and Buncombe counties in North Carolina, 

 whence several tons have been mined during the past few years from 

 granite debris. (Specimen No. 61133, U.S.N.M.) 



Uses. See under monazite, p. 383. 



6. SPODUMENE AND PETALITE. 



This is an aluminum lithium silicate of the formula LiAl (SiO 3 ) 2 , = 

 silica, 64. 5 per cent; alumina, 27.4 per cent; lithia, 8. 4 per cent; in nature 

 more or less impure through the presence of small amounts of ferrous 

 oxide, lime, magnesia, potash, and soda. Luster vitreous to pearly; 

 colors white, gray, greenish, yellow, and amethystine purple. Trans- 

 parent to translucent. Usual form that of flattened prismatic crystals, 

 with easy cleavages parallel with the faces of the prism. Also in mas- 

 sive forms. Crystals sometimes of enormous size, as noted below. 



Mode of occurrence. Spodumene occurs commonly in the coarse 

 granitic veins associated with other lithia minerals, together with tour- 

 maline, beryls, quartz, feldspar, and mica. The chief localities as 

 given by Dana are as below: 



In the United States, in granite at Goshen, Massachusetts, associated at one locality 

 with blue tourmaline and beryl; also at Chesterfield, Chester, Huntington (formerly 



