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Soil Survey Manual - Table 3-12

Classes of surface stones and boulders in terms of cover and spacing

Class Percentage Distance  in meters between stones Name
0.25 m1 0.6 m 1.2 m
1 0.01 - 0.1 ≥ 8 ≥ 20 ≥ 37 Stony or bouldery
2 0.1 - 3.0 1 - 8 3 - 20 6 - 37 Very stony or very bouldery
3 3.0 - 15 0.5 - 1 1 - 3 2 - 6 Extremely stony or extremely bouldery
4 15 - 50 0.3 - 0.5 0.5 - 1 1 - 2 Rubbly
5 50 - 90 < 0.3 < 0.5 <1 Very rubbly

1. 0.38 m if flat