24 ^EW YORK STATE MUSEUM 



rock. Elsewhere the pegmatite shows intrusive relations with the 

 county rocks, forming dikes and bosses with well-defined walls. 



The feldspar is predominantly a potash variety, that is either 

 orthoclase or microcline, but soda feldspar or albite and the lime- 

 soda varieties are frequently represented. Microcline is by far 

 the commoner of the potash feldspars in the New York locaUties. 

 For pottery purposes it is an advantage to have the feldspar in 

 large well-segregated crystals or masses so that it can be readily 

 freed from the accompanying minerals. In the pegmatites w^hich 

 are quarried for pottery spar, the crystals range up to 3 or 4 feet 

 in diameter. The pegmatites of finer texture and those in whicii 

 the minerals are intimately intergrown have application principally 

 for roofing material. 



Quartz is an important ingredient of all pegmatites and if ob- 

 tainable in pure condition may also have value. It is an important 

 by-product, for example, of the Bedford quarries. It occurs in 

 irregular masses, seldom showing any traces of crystal form, and 

 is of gray, white, or pink color. When intergrown with the feld- 

 spar to any extent it detracts from the value of the latter for pot- 

 tery use, though quartz is a necessary ingredient of the pottery 

 mixture. 



The accessory constituents of the pegmatites include a varTe^y 

 of minerals of which the commoner are the micas, hornblende, 

 pyroxene, and tourmalin, while of less frequent occurrence are 

 garnet, magnetite, pyrite, epidote, titanite, and beryl. Black tour- 

 malin is nearly always present in the Adirondack pegmatites. 

 These constituents may be of determinative importance with ref- 

 erence to the commercial value of a pegmatite occurrence, since if 

 disseminated through the mass they preclude the extraction of 

 high-grade material. 



The only feldspar quarries that have been worked during the 

 past year are situated in Westchester and Essex counties. Those 

 near Bedford, Westchester county, have yielded most of the higher 

 grade product used for pottery and enamel ware ; they are operated 

 by P. H. Kinkel's Sons. They are opened in a large mass of peg- 

 matite that outcrops on the eastern and northern slopes of the hill 

 lying a little south of Bedford village. In addition to the feldspa* 

 there is a considerable output of quartz which is sold for wood 

 filler. The feldspar is shipped in three grades, of which no. i 



