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MIT classification system

Short answer

MIT classification is a textural system based on particle size: gravel >2 mm, coarse sand 2–0.6 mm, medium sand 0.6–0.2 mm, fine sand 0.2–0.06 mm, silt 0.06–0.002 mm, clay <0.002 mm. The sand–silt boundary is 0.06 mm, differing from the International system’s 0.02 mm.

Describe the soil classification according to the MIT classification system, giving the grain size ranges of the different soil types.

The MIT (Massachusetts Institute of Technology) classification is a textural system that names a soil only by its particle size. It was proposed by Gilboy and Casagrande and later adopted by the British Standards. The soil is divided into gravel, sand, silt and clay.

Soil typeParticle size (mm)
Gravel> 2.0
Coarse sand2.0 - 0.6
Medium sand0.6 - 0.2
Fine sand0.2 - 0.06
Coarse silt0.06 - 0.02
Medium silt0.02 - 0.006
Fine silt0.006 - 0.002
Clay< 0.002
  • The gravel-sand limit (2 mm) and the clay limit (0.002 mm) are the same as in the International (Atterberg) system, but the sand-silt boundary differs: 0.06 mm in MIT against 0.02 mm in the International system. So MIT silt (0.06 - 0.002 mm) covers a wider range than International silt (0.02 - 0.002 mm).
  • A mixture is named by its major fraction, for example "silty sand" or "sandy clay".
  • Limitation: it ignores plasticity, so soils with the same size distribution can behave very differently.

✓ Answer checked by Claude Opus 5.5 (high effort)

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