THE NONMETALLIO MINERALS. 469 



files and points. Dentists use particularly the "knife blade," a very 

 thin, broad slip of stone, triangular in section, with one short side, the 

 other two forming a thin edge as they come together (Specimens Nos. 

 38998, 53721, U.S.N.M.). They are used for filing between the teeth. 

 Carvers use wedge-shaped, flat, square, triangular, diamond-shaped, 

 rounded, and bevel-edged files for finishing their work. (Specimen No. 

 38996, U.S.N.M.). Jewelers, especially manufacturing jewelers and 

 watchmakers, use all these forms of files and also points. These last 

 are sometimes made the size of a lead pencil, having a cone-shaped end, 

 and are about 3 inches long and i inch square, tapering to a point. 

 They are used chiefly in manufacturing watches to enlarge jewel holes 

 (Specimens Nos. 38995, 53726-53727, U.S.N.M.). 



Wheels of various thicknesses and diameter are also made from 

 Arkansas stone. They are used chiefly by jewelers and dentists, but 

 could be made of service in all workshops where an Arkansas whet- 

 stone is used (Specimens Nos. 38992, 38962, 53710, U.S.N.M.). The 

 difficulty of obtaining pieces of clear stone large enough for wheels 

 several inches in diameter makes the price very high, and the difficulty 

 of cutting out a circular form increases the cost. Wheels are quoted 

 at from $1.10 to $2.20 an inch of diameter. 



Arkansas stone is used for finishing and polishing metal rolls, jour- 

 nals, cross-head slides, piston rods, crank pins, and all kinds of lathe 

 work. 



Fragments of the Arkansas stone are saved at the factories, and now 

 and then sent away to be ground for polishing powder. In the manu- 

 facture of this powder millstones are worn out so rapidly that the 

 process is rather expensive, but as waste stone is utilized, the powder 

 can be sold by the barrel at 10 cents a pound. It makes a very fine, 

 pure white powder of sharp grit, suitable for all kinds of polishing 

 work; it is known as "Arkansas powder." A large amount of energy 

 is wasted, however, in the manufacture of this powder, for the silica 

 of the Ouachita stone is in every way identical with that of the Arkan- 

 sas stone, and it would be much more easily reduced to powder than 

 the Arkansas. 



The so-called Turkish oilstone from Smyrna, in Asia Minor, is both 

 in structure and abrasive qualities quite similar to the Arkansas novac- 

 ulites. (Specimens Nos. 38956, 38967, 38997, U.S.N.M.) It, however, 

 is of a drab color and carries an appreciable amount of free calcium 

 carbonate and other impurities, as shown by the analysis given below, 

 as quoted by Griswold: 



TURKEY STONE. 



Silica (SiO 2 ) 72.00 



Alumina (A1,O S ) 3. 33 



Lime (CaO) 13.33 



Carbonic acid (CO,) 10.33 



