436 JOSEPH HYDE PRATT 



The production of crystalline quartz that is included under 

 the head of abrasives, is that which is used in the manufacture 

 of sandpaper, scouring soaps, and as a wood finisher. In ad- 

 dition to these uses there are large quantities of quartz sand 

 used in the stonecutting trade, especially by the marble work- 

 ers. A small amount of quartz is pulverized, and sold under 

 the name of tripoH. 



Among the abrasives, infusorial earth and tripoli formed 

 but a small proportion of the production, and of the amount 

 produced less than half was actually used for abrasive pur- 

 poses. Under the head of infusorial earth and tripoli are in- 

 cluded all porous, siUceous earths of organic origin, such as 

 infusorial earth, diatomaceous earth and tripoli, and also a 

 siHceous material which is the residue from an impure siliceous 

 hmestone by the leaching out of the calcium carbonate. The 

 material now produced is from CaHfornia, Georgia, Maryland, 

 Missouri, New Hampshire, New York and Virginia. 



The production of pumice in the United States has been 

 very erratic, although commercial deposits are known to oc- 

 cur in large quantity, especially in Utah and Nebraska. On 

 account, however, of the distance of these deposits from the 

 railroad, and from the large markets, they are not able to com- 

 pete with the pumice imported from Lipari, Italy, which is 

 shipped largely as ballast, and which, after being ground and 

 bolted, is sold in New York at from 2 to 2| cents per pound. 

 These Lipari deposits supply almost the entire demand for 

 pumice. 



The natural abrasives that have the highest abrasive effi- 

 ciency are corundum and emery, and there is an increasing 

 demand for these, which is due largely to the increase in man- 

 ufacturing, especially of agricultural machines, but also to 

 the improved methods that have been devised for making em- 

 ery and corundum stones and wheels of all shapes and sizes. 

 These abrasives, manufactured into wheels of various sizes, 

 have replaced, to some extent, the smaller grindstones in man- 

 ufacturing estabhshments. They have also been manufactured 

 into oilstones and whetstones, and have successfully competed 

 with the natural product, although selling at a higher price. 

 With the exception of certain emery wheels made by the sili- 



