Table 3. Soil structure

Type Kind Class Size(mm)
1. Structureless - no observable aggregation or no definite orderly arrangement around natural lines of weakness. A. Single grain - loose, incoherent mass of individual particles as in sands.    
B. Amorphous (massive) - a coherent mass showing no evidence of any distinct arrangement of soil particles.    
2. Blocklike-soil particles arranged around a point and bounded by flat or rounded surfaces. A. Blocky (angular blocky)- rectangular and flattened, vertices sharply angular Fine blocky, <10
Medium blocky, 10-20
Coarse blocky, 20-50
Very coarse blocky >50
B. Subangular blocky-faces subrectangular, vertices mostly oblique, or subrounded. Fine subangular blocky, <10
Medium subangular blocky, 10-20
Coarse subangular blocky, 20-50
Very coarse subangular blocky >50
C. Granular-spheroidal-characterized by rounded vertices. Fine granular, <2
Medium granular, 2-5
Coarse granular, 5-10
3. Platelike-soil particles arranged around a horizontal plane and generally bounded by relatively flat horizontal surfaces. A. Platy-horizontal planes more or less developed. Fine platy, <2
Medium platy, 2-5
Coarse platy, >5
4. Prismlike-soil particles arranged around a vertical axis and bounded by relatively flat vertical surfaces. A. Prismatic-vertical faces Fine well defined and edges sharp. Fine prismatic, <20
Medium prismatic, 20-50
Coarse prismatic, 50-100
Very Coarse prismatic, >100
B. Columnar-vertical edges near top of columns not sharp. (Columns may be flat-topped round-topped, or irregular). Fine columnar, <20
Medium columnar, 20-50
Coarse columnar, 50-100
Very Coarse columnar, >100