Density or Consistency, Hardness
Use the following charts to determine the density or consistency and hardness of material encountered.
Density (Cohesionless) | Consistency (Cohesive) | TCP Values | Field Identification |
|---|---|---|---|
Very loose | Very soft | 0 to 8 | Core (height twice diameter) sags under own weight |
Loose | Soft | 8 to 20 | Core can be pinched or imprinted easily with finger |
Slightly compact | Stiff | 20 to 40 | Core can be imprinted with considerable pressure |
Compact | Very stiff | 40 to 80 | Core can be imprinted only slightly with fingers |
Dense | Hard | 80 to 5 in./100 | Core cannot be imprinted with fingers but can be penetrated with pencil |
Very dense | Very hard | 0 in. to 5 in./100 | Core cannot be penetrated with pencil |
Mohs’ Hardness Scale | Characteristics | Examples | Hardness | Approximate TCP Values |
|---|---|---|---|---|
5.5 to 10 | Rock will scratch knife | Sandstone, chert, schist, granite, gneiss, some limestone | Very hard | 0 in. to 2 in./100 |
3 to 5.5 | Rock can be scratched with knife blade | Siltstone, shale, iron deposits, most limestone | Hard | 1 in. to 5 in./100 |
1 to 3 | Rock can be scratched with fingernail | Gypsum, calcite, evaporites, chalk, some shale | Soft | 4 in. to 6 in./100 |