256 NEW YORK STATE MUSEUM 



matter which has not been adequately considered in the discussion 

 hitherto is the amount of waste which would have to be dealt 

 with in the working of most feldspar deposits. These are in the 

 nature of coarse granites and carry quartz and other minerals 

 besides the feldspar. Furthermore, very few occurrences contain 

 the potash varieties alone (microcline and orthoclase) but usually 

 they have considerable, if not important, amounts of the soda-lime 

 varieties or the plagioclases. In nearly all the New York State 

 occurrences the common variety of potash spar is microcline. 

 Orthoclase is a rarity. The microcline often is intergrown with 

 the soda variety (albite) in such manner that the two can not be 

 mechanically separated, and thereby the potash content is brought 

 down very considerably below the amount required by the chemical 

 formula for microcline. 



There were no important developments in the production of 

 feldspar for pottery and other established uses, and the output, as 

 reported, of 16,240 long tons valued at $82,461 showed no material 

 change from the total of the preceding year. The figures are 

 inclusive of unsorted pegmatite, which is shipped by two quarries 

 in the Adirondacks for roofing and other purposes. The active 

 quarries included two in Essex county, one in Fulton and one in 

 Westchester county. 



A detailed account of the feldspar resources of the State was 

 incorporated in the report of the New York State Museum, entitled 

 " The Quarry Materials of New York," published in 1916. There 

 is an abundance of the mineral among the crystalline formations 

 of the Adirondacks and the Highlands, where it occurs in " giant 

 granites " or pegmatite intrusions, some of which attain large size. 

 Only a few of the large occurrences have so far been developed. 

 The market for feldspar and the prices obtainable do not encourage 

 extensive exploitation of the resources, and only under favorable 

 conditions can deposits be profitably worked. 



Among the factors that have to be taken into consideration in 

 determine the possibilities of a particular occurrence, some relate 

 to the intrinsic characters of the deposit which require more or 

 less expert knowledge to determine. The geological features are 

 important in relation to the form and probable extent of the body, 

 since there is almost every variation in these respects to be met 

 with among pegmatites. Tabular bodies or dikes, with parallel walls 

 and of indefinite continuity downward, are rather the exception 

 than the rule in the large workable occurrences. More commonly 



