AGI DATA SHEET 17.1 Grain-size Scales By Roy L. Ingram, University of North Carolina GRAIN-SIZE SCALE USED BY AMERICAN GEOLOGISTS Modified Wentworth Scale - after Lane, et al., 1947, Trans. American Geophysical Union, v. 28, p. 936-938 GRADE LIMITS U.S. phi mm mm inches Standard Sieve Series GRADE NAME -12 4096 - - 161.3 - very large -11 2048 - - 80.6 - large -10 1024 - - 40.3 - medium Boulders -9 512 - - 20.2 - small -8 256 - - 10.1 - large Cobbles -7 128 - - 5.0 - small GRAVEL -6 64 - - 2.52 63 mm very coarse -5 32 - - 1.26 31.5 mm coarse -4 16 - - 0.63 16 mm medium Pebbles -3 8 - - 0.32 8 mm fine -2 4 - - 0.16 No. 5 very fine -1 2 - - 0.08 No. 10 very coarse 0 1 - - 0.04 No. 18 coarse +1 1/2 0.500 - - No. 35 medium Sand SAND +2 1/4 0.250 - - No. 60 fine +3 1/8 0.125 - - No. 120 very fine +4 1/16 0.062 - - No. 230 coarse +5 1/32 0.031 - - medium Silt +6 1/64 0.016 - - fine +7 1/128 0.008 - - very fine +8 1/256 0.004 - - coarse MUD +9 1/512 0.002 - - medium Clay size +10 1/1024 0.001 - - fine +11 1/2048 0.0005 - - very fine -12 1/4096 0.00025 AGI-DS-rvd-82