Manufactured sand is essentially the finely crushed rock. It may be simply screenings from coarse aggregate crushing, or crushed specifically for the purpose. The characteristics of manufactured sand reflect those of the parent rock; the durability properties are sometime similar to those of the coarse aggregate from the same source, but often may be different.
The finely crushed rock is screened and the screenings re-combined to produce gradations similar to those of a well-graded natural sand. The process often produces a large volume of fines (powdered rock passing the 100 and 200 sieves) that, as of now, has limited practical use, and must be disposed into the quarry or land fill.
The fine crushing must produce an equidimensional particles. Many rock types have a tendency to produce flat, elongate particles that do not form a compact framework.
