THE NONMETALLIC MINERALS. 463 



XIV. MISCELLANEOUS. 



1. Grindstones; Whetstones; and Hones. 



The custom of sharpeniiig- edge tools on pieces of stone has been 

 practiced by barbarous and civilized nations ever since the adoption of 

 cutting- implements of any kind, however crude and of whatever 

 materials. 



With the tirst crude implements, it is s;ife to say almost any stone 

 possessing the riMiuisite grit would serve to produce the rough edge 

 desired. With the improvement in the cutting implement there has, 

 however, been necessitated a corresponding improvement in the char- 

 acter of the sharpening implement as well. Formerly, it may be safely 

 assumed, everv man used that which was most accessible and could be 

 made to best answer its purpose. Now the grindstone and whetstone 

 industr}" is as well organized as any other branch of manufacture, and 

 forms no inconsiderable feature of the nation's trade. Localities are 

 ransacked and material is brought from far and near, carried long dis- 

 tances, overland or across the ocean, to the workshops of the manu- 

 facturer to be cut into the desired shapes and sizes, classified and 

 assorted according to quality, and sent abroad once more to meet the 

 demands of the ever-increasing trade. The use of the grindstone, it 

 should be noted, is not confined merely to sharpening edge tools, but, 

 as will be noted later, they are made from a variety of materials and 

 of an equal variety of sizes, from the 2-inch wheel of novaculite, used 

 by jewelers, to a coarse grit monster of over 2 tons weight for the 

 grinding of rough castings in machine shops. 



A stone to be suitable for grinding purposes must possess a fine and 

 even grain, free from all hard spots and inequalities of any kind. It 

 is essential, too, that the various particles of which it is composed be 

 cemented together with just sufiicient tenacity to impart the neces- 

 sary strength to the stone, and yet allow them to crumble away when 

 exposed to friction, thus continually presenting fresh sharp grains and 

 surfaces to act upon the material being ground. Simple as these 

 essential qualities may seem they are in reality but rarely met with 

 in perfection, and the majority of grindstones now on the market are 

 quarried from a comparatively limited number of sources. If the 

 stone be too friable it wears away too rapidly, and the grinding done 

 is coarse and uneven; a sharp edge or polish is unobtainable. If too 

 hard it glazes and loses its cutting qualities, or cuts so slowly as to be 

 no longer desirable. If, moreover, the particles composing the stone 

 adhere with too little tenacit}^, the stone, particularly if it be a large 

 one, such as is used for grinding castings, is liable to burst, perhaps 

 to the serious injury of workmen and machinery. 



The requisite qualities as above enumerated are found mainly in 



