1 86 NATURE STUDY. 



Some Abrasives. 



BY WILLIAM H. HUSE. 



A class of stones, of interest because of their cpmmercial 

 value, is the group used as abrasives. These stones are 

 necessarily hard in order to abrade, and must also be more 

 or less coarse grained that the surface of the abrasive may 

 wear away and not become glazed. It has been the privi- 

 lege of the writer to recently examine specimens from the 

 Pike Manufacturing Company of Pike, N. H., and these 

 will be briefly described. 



The coarsest grained is a sandstone from Indiana, near 

 Orleans. While coarse grained as a whetstone it is not 

 the coarsest variety' of sandstone. It is colored a light 

 graj'ish-brown by a small quantity of oxide of iron. It is 

 so much used bj' the shoe trade that it is often called 

 " shoemakers' sandstone." It is also used in the kitchen 

 for sharpening the common knives used there. 



Hindostan is the name of a very fine grained sandstone, 

 also from Indiana, a little lighter than the first named, 

 and rather soft. This is efhcient as a cheap stone for gen- 

 eral purposes. 



Washita is a quartzite from Hot Springs, Arkansas, 

 quite fine grained and nearly white in color, some brands 

 quite so. One variety is streaked with reddish and re- 

 ceives a commercial name descriptive of its color. This 

 stone is used to sharpen general woodworking tools. 



Arkansas stone is chemically the same as the last named 

 but is much finer grained. It is perhaps the hardest and 

 finest grained sharpening stone that is used in its natural 

 state. This is known to the mineralogist as novaculite, 

 and as the student in mineral determination uses it to find 

 the streak of the specimen he is studying he calls his nov- 

 aculite whetstone a " streakstone." This mineral is found 



