This Digest is concerned only with sands that occur naturally as distinct from the fine aggregates obtained by crushing stone, brick or other material. Next to bricks and gravel, more sand is used than any other material in building; and, of this, the greater proportion is used in concrete. Yet the quality of sand does not always receive the attention it deserves - a neglect responsible for many failures. The emphasis of attention has partly shifted from the size grading of concrete aggregate to its specific surface area, which has a more direct influence on mix characteristics. This and other criteria are here discussed in relation to the designer's specification and the builder's selection of concreting sands.