UNITED STATES MINERAL RESOURCES 



SILICA SAND 



By Keith B. Ketner 



CONTENTS 



Psee 



Abstract of conclusions 577 



Introduction 577 



Exploitation 578 



Geologic environment 578 



Resources 579 



Problems for research 579 



Selected references 580 



FIGURE 



65. Graph showing production of silica sand in the 

 United States, 1930-70 



578 



ABSTRACT OF CONCLUSIONS 



Silica-sand formations and the quartz sandstones from 

 which silica sand and silicon are mainly derived are abund- 

 antly distributed throughout the United States and the 

 world. Although the use of silica-sand, principally in the 

 glass and metallurgical industries, is rapidly increasing, 

 shortages that might cause heavy reliance on imports are 

 not likely. Problems are caused if urban development pre- 

 empts the surface over valuable silica sand deposits and if 

 abandoned sandpits are left in a useless condition. Urban 

 planners can solve the first problem by restricting important 

 sand deposits from other long-term uses, and industry can 

 solve the second by contouring the disturbed surface for 

 productive or recreational use. More detailed geologic in- 

 vestigations in urban areas are needed to precisely delineate 

 silica-sand deposits in advance of urban development. 



INTRODUCTION 



Natural sands can be composed of siliceous rock 

 fragments and various silica-bearing minerals, but 

 the term "silica sand" is generally understood to 

 mean sand composed almost entirely of SiOs in the 

 form of mineral quai'tz. This type of sand is also 

 called special or industrial sand. Cemented silica 

 sand is called quartz sandstone or quartzite. Some 



quartz sandstones can be easily broken down to their 

 original state of loose sand either because they were 

 never very firmly cemented or because the cement 

 has been almost entirely dissolved by weathering 

 processes. Sandstones softened by weathering are a 

 principal source of silica sand. Silica sand can be 

 made by crushing and grinding hard quartz sand- 

 stones or quartzites, but the result tends to be more 

 expensive than natural sands. 



Silica sand of extraordinary purity is required in 

 the manufacture of clear glass and sand of moder- 

 ately high purity is required in the manufacture of 

 brown or green glass and in certain uses, such as 

 sandblasting, glass grinding, water filtration, rail- 

 road traction, and oil-well rejuvenation. Silica sand 

 of moderately high purity with a natural or added 

 bonding material is used in making metallurgical 

 molds and furnace linings. Ground silica sand is a 

 major component of ceramic ware. The use of 

 siliceous raw materials as a source of metallic sili- 

 con is not treated here but is discussed by Brantley 

 (1970). 



The glass and metallurgical industries consume 

 more than 20 million tons of silica sand per year, 

 and other users consume about 10 million tons. The 

 rate of consumption is increasing rapidly. 



Certain relatively expensive natural and artificial 

 aluminous abrasives can be substituted for quartz 

 in blasting sand and glass-grinding sand, but for 

 other uses no satisfactory substitute for high-silica 

 sand has been found. 



The quartz content of many impure sands can be 

 raised by beneficiation — the elimination of unde- 

 sirable impurities such as clay, rock fragments, and 

 iron-bearing minerals. Beneficiation techniques are 

 well known and to some extent are in current use. 

 These include screening, washing with water, leach- 

 ing with acid, flotation, and various methods that 

 take advantage of differences in specific gravity 

 between quartz and some of the contaminating 



U.S. GEOL. SURVEY PROF. PAPER 820 



577 



