THE NONMETALLIC MINERALS. 288 



parallel with tho strike of the gneissoid si-hists in which it lies, i. e, 

 northeast and southwest. Th(> vein material is ((uartz, feldspar, and 

 miea. Tlie ipiarry, as des('ri])ed by R. L. Packard, is in the form of an 

 open cut in the hillsi(U% heino- some 300 feet long- by 100 feet wide, 

 and of very irregular contours. The present floor and the sides of the 

 cut are of feldspar (Specimen No. (51086, LI.S.N.M.), containing irreg- 

 ular bodies of quartz and mica, the first named occurring in large masses 

 entirely free from other minerals, though a second grade is taken 

 out which is in reality an intimate mixture of quartz and feldspar. 



The quartz occurs, besides as mentioned above, in the form of irreg- 

 ular bodies, sometimes 6 or 8 feet across and 15 feet or more long. It 

 also occurs in cavities, or geodes, in the form of flattened crystals 

 (Specimen No. 61085, U.S.N.M.). The mica is hereof little economic 

 importance, being found in the mass of the feldspar and along the seams 

 in the form of narrow, lanceolate masses, often arranged in small radi- 

 ating conical forms with their apexes outward. 



The principal feldspar quarries thus far worked are in the Eastern 

 United States, from Maine to New Jersey. The material is mined from 

 open cuts, being blasted out with powder and separated from adhering 

 quartz, mica, and other minerals by hand, after which it is shipped in 

 the rough to the potteries, or in some cases ground and })olted in the 

 near vicinity. In Connecticut the material has in times past been 

 ground by huge granite disks mounted like the wheels of a cart on an 

 axle through the center of Avhich extended a vertical shaft. By the 

 slow revolution of this shaft the wheels traveled around in a limited 

 circle over a large horizontal granite slab. The pieces of spar being 

 placed upon the horizontal slab were thus slowly ground to powder, 

 after which it was bolted and sacked. The modern method of pulver- 

 izing is by means of the so-called "Cyclone" crusher. The value of 

 the uncrushed material delivered at the potteries is but a few dollars 

 a ton. Hence, while there are unlimited quantities of the material in 

 different parts of the Appalachian region, but few are so situated as 

 to be profitably worked. 



LL'ies. — The feldspars are used mainly for pottery, being mixed in 

 a finelv pulverized condition with the kaolin or clay. When subjected 

 to a high temperature the feldspar fuses, forming a glaze and at the 

 same time a cementing constituent. There are other substances more 

 readily fusible which are utilized for this purpose in the cheaper kinds 

 of ware, but it is stated that in the highest grades of porcelain, as 

 those of Sevres, feldspar is the material used. The proportions used 

 vary with different manufacturers, each having adopted a formula best 

 adapted for his own workings. 



2. Micas. 



Under this head are comprised a number of distinct mineral species, 

 alike in crystallizing in the monoclinic system and having a highly 



