The silica contents of nine common sands calculated from mineralogic analyses are compared with the silica contents determined by chemical analyses. The maximum difference, a deficiency of 2.46 per cent in the mineralogic analyses was for a sand containing 89.8 per cent silica by chemical analysis. The differences decrease with increasing silica content, although not in a very regular way. The maximum silica content by chemical analysis, namely, 96.03 per cent, differs by 0.78 per cent from the corresponding silica content in the mineralogic analysis. A short method of mineralogic analysis gives results that differ by a minimum of 0.39 per cent and a maximum of 2.50 per cent from the results obtained by a detailed mineralogic analysis. The detailed mineralogic analyses show: (1) The percentage of silica in the heavy mineral portion is fairly regularly inversely proportional to the percentage of heavy minerals in the sands. (2) The abundance of grains of the different minerals in the various grain sizes varies regularly with some minerals and irregularly with others. Some minerals, e.g., zircon, are markedly confined to certain sizes. (3) Minerals with good cleavage are not uniformly more abundant in the smaller grain sizes. Kyanite, for example, was found to be regularly more abundant in the larger grain sizes.

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