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Blast sand is that used for “sand-blasting.” The properties 
making it suitable for this purpose depend upon the nature 
of the object on which it is to be used. The term is applied 
to natural sand and to crushed quartz. 
Glass sand is a high silica sand employed in the making of 
glass. The term is applied to natural sand and to crushed 
sandstone, quartzite, or quartz. 
Fire sand is a highly refractory sand. 
Moulding sand is that used in forming the moulds in which 
iron, brass, and other metals are cast. 
Silica sand, as pointed out before, is that consisting almost 
entirely of quartz. 
Silver sand is a pure white, sharp, silica sand or crushed 
quartz. It is used for sand-blasting on glass and silver ware. 
Finely ground quartz is very often spoken of as silex. 
USES. 
Smelting. In the smelting of some ores containing basic 
gangue, quartz is introduced into the furnace charge as a 
flux. The quartz used for this purpose may be vein quartz, 
quartzite, or sandstone. If it contains metallic values, it should 
be classed as an ore having desirable properties for mixing pur 
poses; but if it is barren it must be considered merely as a flux. 
The quartz is delivered to the smelter as it comes from the 
quarry, or it may be crushed to any specified degree of fineness. 
Crushed quartz is used as a material for lining certain metal 
lurgical furnaces. 
Foundries. A moulding sand should be of fairly uniform 
fineness and contain sufficient clay to give it body and strength 
to withstand the withdrawal of the patterns, the handling of 
the moulds, and the action of the molten metal. It should be 
sufficiently porous to allow the escape of the gases developed 
by the hot metal. It should be refractory, otherwise it would 
sinter, closing up its pores and thus preventing the escape of 
gases, as well as fusing to the surface of the metal causing ugly 
castings which would not machine easily. The presence of 
lime is objectionable, as it tends to lessen the refractoriness and