grain size, igneous rocks

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grain size, igneous rocks Arbitrarily defined limits for the sizes of crystals within an igneous rock. Commonly accepted grain-size ranges are:

Very coarse

>3 cm

Coarse

5 mm to 3 cm

Medium

1–5 mm

Fine

<1 mm

Glassy

no grains present



For sedimentary rocks, see PARTICLE SIZE.

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