An index of fineness or coarseness of an aggregate sample. An empirical factor determined by adding total percentages of an aggregate sample retained on each of a specified series of sieves, and dividing the sum by 100. Note: US Standard sieve sizes are used: No. 100, No.50, No. 30, No. 16, No. 8, and No. 4, and 3/8 in., 3/4 in., I in., 2 in., 3 in., and 6 in.