MINERAL RESOURCES OF THE STATE OF NEW YORK 219 



ocoimng either alone or as gangue for ores. In the form of chert, 

 a micro-crystalline variety, it is associated with some limestones. 

 Quartz possesses qualities of hardness, toughness and resistance to 

 chemical change matched by relatively few other minerals. 



Despite the abundance of materials containing quartz in large 

 amounts, the supplies of high-grade silica adapted to certain 

 important industrial uses are not so common but that they possess 

 extensive interest and value. One of the more persistent impurities 

 of great importance in determining the commercial availability of 

 deposits is iron which may always be counted upon as present in 

 one form or another. It may be carried by finely divided iron 

 oxides, or by admixture with some iron-bearing siEcate like biotite, 

 hornblende or pjnroxene. 



Uses. The manufacture of glass requires large amounts of high- 

 grade quartz. To be suitable for most kinds of glass, the material 

 should contain 98.5-99 per cent of silica as a minimum. The 

 restrictions with regard to iron are rigid; for plate and window glass 

 the usual limit is 0.2 per cent ferric oxide, equivalent to 0.14 metallic 

 iron, and for optical glass nothing more than a trace is allowable. 

 A granular material is best adapted to this purpose, and consequently 

 sands and loosely textured sandstones easily reducible to granular 

 state are mostly used. Sands that are not suitable in their natural 

 state may sometimes be beneficiated by washing and screening. 

 The size should be also fairly uniform and not too coarse; a sand 

 that ranges from 20 to 50 mesh is preferred. 



Pottery manufacture also requires a high-grade quartz low in 

 iron. Vein quartz or a micro-crystalline quartz something like 

 flint is used and has to be finely ground. 



The manufacture of silicon and ferro-silicon has become quite an 

 important industry in the State, and has developed a local market 

 for material suited to the purpose. A silica content of 96 to 97 

 per cent is required; the limitations otherwise are not particularly 

 rigid. A quartz sandstone or quartzite is employed by most of the 

 plants in the State and there are abundant suppHes to be had in the 

 Potsdam and other foimations. 



Quartz is an important refractory material in metallurgy. It is 

 employed in the form of quartzite and quartz schist (ganister) for 

 the lining of shaft furnaces and as sand (fire sand) for open-hearth 

 ftunaces, ladles etc. 



Among the other uses of quartz are as an abrasive, wood-filler and 

 as an ingredient of paints. For sand-paper vitreous or vein quartz 

 is crushed and sized. The purity is not so important, but the quartz 



