has part has quality clay EcoLexicon:clay Particulate environmental material which 1) is composed primarily of clay particles, with only minor proportions of other materials, 2) demonstrates plasticity when wet, and 3) is capable of hardening when dried or fired. SWEETRealm:Clay This definition is intentionally ambiguous to support the multiple thresholds set by different authorities.The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider the separation to occur at a particle size of 2 μm (clays being finer than silts), sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg limits. ISO 14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. Mixtures of sand, silt and less than 40% clay are called loam. Similar mixtures with greater than 40% clay are often considered clay soils. silt particulate environmental material particle of clay porous