QUARTZ ROCK. 359 



and waxy in luster when polished, presenting grayish and 

 greenish colors and other shades. Gr=2*8 — 2*9. It has a 

 greasy feel. It consists of silica 55*0, alumina 30'0, potash 

 7*0, water 3 to 5 per cent., with a trace of oxyd of iron. It 

 is carved into images, and is hence called figure-stone. 



QUARTZ ROCK. 



Quartz rock is a compact rock consisting of quartz, and 

 often appearing granular. Its colors are light gray, reddish 

 or dull bluish ; also sometimes brown. 



When the granular quartz contains a little mica, it often 

 breaks in slabs like gneiss or mica slate. The itacolumite 

 of Brazil, with which gold and topaz are associated, is a 

 micaceous granular quartz rock of this kind. 



Flexible sandstone is an allied rock of finer texture. It owes 

 its flexibility to the mica present, and its looseness of aggre- 

 gation. Granular quartz graduates into the proper sandstones, 

 which are treated of for convenience on a following page. 



Granular quartz is one of the most refractory of rocks. It 

 is consequently used extensively for hearthstones, for the 

 lining of furnaces, and for lime kilns. At Stafford, Conn., 

 a loose grained micaceous quartz rock is highly valued for 

 furnaces ; it sells at the quarry for 16 dollars a ton.* 



Granular quartz is also used for flagging, and a fine 

 quarry is opened in Washington, near Pittsfield, Mass. ; it 

 also occurs of good quality at Tyringham and Lee, Mass. 

 In the shape of cobble stones, it is a common paving material. 



A highly important use of this rock is in the manufacture 

 of glass and sandpaper, and for sawing marble. In many 

 places it occurs crumbled to a fine sand, and is highly con- 

 venient for these purposes. In Cheshire, Berkshire county, 

 Mass., and in Lanesboro', Mass., it occurs of superior qual- 

 ity, and in great abundance. It is also in demand for the 

 manufacture of glass and pottery. In Unity, N. H., a gran- 

 ular quartz is ground for sandpaper and for polishing powder ; 

 the latter is a good material for many purposes. 



A fine variety of granular quartz is a material much 

 Valued for whet-stones. 



BUHRSTONE. 



Buhrstone is a quartz rock containing cellules. It is ai 

 hard and firm as quartz crystal, and owes its peculiar value 



* Rep. on Connecticut, by C. U. Shepard — p. 78. 



