De afronding van kwartskorrels in podsolprofielen

The origin of rounding and frosting of quartz grains is discussed. To test if soil processes play an important role, samples from A-, B- and C-zones of sandy podsolic soils were taken in 18 localities. In the preparation of the samples no chemicals were used. Hundred quartz grains of the sieve fraction 355-500 micrometer were divided into 5 roundness classes and studied under the microscope. It appeared that in the A-zone more well rounded and frosted quartz grains are found, in some cases even twice as much as in the C-zone, which is the unchanged cover sand. Thus the importance of humic acids in soil processes as an agent creating rounded and frosted quartz grains has been demonstrated.