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. Standard GRADE NAME phi mm mm inches Sieve Series -12 4096 - - - 161.3 - - - -11 2048 - - - 80.6 - - - very large -10 1024 - - - 40.3 - - - large -9 512 - - - 20.2 - - - medium Boulders -8 256 - - - 10.1 - - - small -7 128 - - - 5.0 - - - large -6 64 - - - 2.52 63 mm - - - small Cobbles GRAVEL -5 32 - - - 1.26 31.5 mm very coarse -4 16 - - - 0.63 16 mm coarse -3 8 - - - 0.32 8 mm medium Pebbles -2 4 - - - 0.16 No. 5 fine -1 2 - - - 0.08 No. 10 very fine 0 1 - - - 0.04 No. 18 very coarse +1 1/2 0.500 - - - No. 35 coarse +2 1/4 0.250 - - - No. 60 medium Sand SAND +3 1/8 0.125 - - - No. 120 fine +4 1/16 0.062 - - - No. 230 very fine +5 1/32 0.031 - - - coarse +6 1/64 0.016 - - - medium Silt +7 1/128 0.008 - - - fine +8 1/256 0.004 - - - very fine MUD +9 1/512 0.002 - - - coarse +10 1/1024 0.001 - - - medium Clay size +11 1/2048 0.0005 - - - fine +12 1/4096 0.00025 very fine AGI-D8-rvd-82