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Grain Size Determination

The determination of grain size or particle size distribution is a cumulative frequency distribution of relative amounts of particles in a sample within specified size ranges. The use of sieves and settling tubes to separate a sample based on grain size results in a description of the sample based on particle size and density.
Grain size analysis

The major fractions of particle distribution (based on the Wentworth scale) includes the following classes:

1) cobble (-6 phi and above)
2) gravel (-2 phi to -5 phi)
3) sand (+4 phi to -1 phi), and
4) combination of both silt and clay (+5 phi and below)

Usually for marine sediments, which have a wide range of particle sizes, two different methods are required:

1) Sieving of the large or coarse fraction (> 64 mm or >+4 phi), and
2) Gravimetric pipetting of the fine fraction (< 64 mm or <+5 phi).

The presence of petroleum has an effect on the particle size distribution, skewing to larger sizes. Therefore, petroleum contamination is removed from the sample, using washing agents, before conducting particle size analysis.