coarse-grained . (a) Said of a crystalline rock, and of its texture, in which the individual minerals are relatively large; specif. said of an igneous rock whose particles have an average diameter greater than 5 mm (0.2 in.). Johannsen (1931, p.31) earlier used a minimum diameter of 1 cm, and referred to igneous rocks having walnut-size to coconut-size grains as "very coarse-grained". Syn: phaneritic. (b) Said of a sediment or sedimentary rock, and of its texture, in which the individual constituents are easily seen with the unaided eye; specif. said of a sediment or rock whose particles have an average diameter greater than 2 mm (0.08 in., or granule size and larger). The term is used in a relative sense, and various size limits have been suggested and used. Cf: fine-grained; medium-grained. (c) Said of a soil in which gravel and/or sand predominates. In the U.S., the minimum average diameter of the constituent particles is 0.05 mm (0.002 in.), or, as used by engineers, 0.074 mm (retained on U.S. standard sieve no.200); the International Society of Soil Science recognizes a diameter limit of 0.02 mm. Cf: fine-grained.