ABRASIVE MATERIALS 431 



largest quantities are quarried in Ohio, whenco the jiroduct 

 is shipped to all parts of the United States. Tlie qimrrios in 

 the northern i)art of Ohio are located at Chap;rin l-alls, Bcroa, 

 Cuyahoga Falls, Elyria, Euclid, Grafton, Iii(l(*pendcnce, Maa- 

 sillon. North Amherst, Oberlin, and Peninsula; those in the 

 eastern part of the state at Empire, Frecport, and Tipporanoe; 

 and those in the southern portion of the state at AinoHville, 

 Belpre, Briggsdale, Constitution, Federal, Gravel Bank, Ports- 

 mouth, Vincent and Marietta. A large number of tiie quar- 

 ries in northern and southern Ohio have been Ijrought under 

 one management. At Empire, Peninsula, and Tippecanoe 

 the pulpstone variety of grindstone is found; at the quarries 

 at Empire pulpstone is the chief production, tlie regular grind- 

 stone forming but a very small i)art of the output. 



The quarries in West Virginia are directly across the 

 Ohio river from those in southern Ohio, and are located at 

 Atlantic, Bois, Briscoe, Lonecedar, and Sherman. 



Grindstones in very small quantity have been made for 

 local use near Columbus, Yellowstone county, Mont.; near 

 Rawlins, Carbon county, Wyo.; and near Edgemont, S. Dak. 



Tliere is considerable variation in grindstones, dependent 

 upon the variation of the sandstone from which they are made, 

 which is due (1) to the character of the cementing material — 

 whether it is a hydrous iron oxide, calcium carbonate, or silica; 



(2) to the percentage of the cementing material — that is, 

 whether the grains are separated from each other by simply a 

 minute film of cementing material or by a considerable layer ; 



(3) to the size and shape of the grains of quartz. According 

 to these variations there are at least seven grits that are recog- 

 nized as distinctive, six of which are derived from various 

 grades of Ohio sandstone and one from the Michigan stone. 



It may be w-ell to mention here the grades of grindstones 

 that are imported into the United States, as they are used for 

 special purposes for which they seem to Idc particularly adapt- 

 ed. A grindstone made from a coarse, hard sandstone is im- 

 ported from Bavaria, and is used particularly for nizor grind- 

 ing. A fine, hard grindstone called the Craigleith, is imported 

 from Edinburgh, and is used for special puri:>oses in the glass 

 trade. 



