The ten original samples, (Table 1), had the same grain size
distribution and can be classified as sandy-silt (Shepard, 1954). After
the separation with the improved gravitational method an average
amount of 72 g for silt and 9 g for clay were recovered, giving a total
amount of 726.9 g and 94.1 g respectively. Further analysis was
carried out to check for the silt and clay purity. The purity of the
fraction indicates the amount of the sediment having the particles of
the expected size. The resulting purity was extremely high, being 90%
for silt and 95% for clay.