QUARRY MATERIALS OF NEW YORK 1 59 



purpose it is ground to an impalpable powder, ft also finds use 

 in the manufacture of abrasive wheels as a binder for the emery 

 or carborundum with which the spar is mixed. 



The quartz, which is an important ingredient of the loeal peg- 

 matites, has value if obtainable in fairly pure condition. It is 

 extensively produced at the Bedford quarries. The principal uses 

 are in pottery and in the manufacture of abrasives and wood filler. 

 The requirements for pottery are strict with regard to iron, but 

 less so for other uses. The quartz from pegmatites may be re- 

 garded as a by-product, not of sufficient importance to warrant 

 quarry operations for itself alone. Larger amounts of quartz come 

 from quartz veins. 



The unsorted pegmatite, when crushed, finds sale among makers 

 of prepared roofing, in which it is employed as a surface coating 

 with tar or some bituminous binder. The pegmatite is crushed to 

 a pea size or a little coarser, the feldspar and mica yielding flat 

 surfaces that are of advantage in securing firm adherence to the 

 paper. The purity of the material is a subordinate factor and no 

 effort is made usually to separate any of the ingredients. The fine 

 material resulting from the crushing is sold for use in concrete and 

 grout, and a small proportion in the coarser sizes finds a market 

 as poultry grit. Crushed pegmatite has recently come into use in the 

 preparation oi artificial stone which is made to imitate granite and is 

 cast in almost any form so as to require little or no dressing. 



General considerations. The economic value of pegmatite oc- 

 currences depends upon a number of features, some of which have 

 been mentioned already. The character of the feldspar will deter- 

 mine the adaptability of the product to different uses. In case the 

 minerals are much intergrown, even if in fairly large individuals, 

 the material can hardly be sold for the higher grades without so 

 much expense in sorting and cobbing as to render the operations 

 unprofitable. Such occurrences are adapted only for the production 

 of unsorted pegmatite for roofing and concrete. To enable them 

 to be worked profitably, they must be of large size and conveniently 

 situated for shipment of the product to market. 



Under the varying conditions presented by the occurrence and 

 mineral nature of pegmatites, there is little that can be stated gen- 

 erally in regard to the value of undeveloped properties. As a rule, 

 it may be said that a dike or lens less than 25 feet thick is not 

 workable and one of that size can be worked profitably only under 

 exceptional circumstances. Of course, much depends upon distance 

 of haulage and the freight rates to market. 



