The low-plastic clay from Godthåb, Greenland. An X-ray mineralogical investigation

Abstract

A glacial sediment from Godthab (Greenland) had very low plasticity and coherence in spite of its high content of particles smaller than 2 μ. A sample was separated quantitatively into fractions of sand, silt and clay, and the mineralogical composition of each fraction was determined chiefly by X-ray powder methods. The composition of the sample was in fair agreement with that of the surrounding rocks.

As a whole the sample was poor in quartz but rich in oligoclase, hornblende, biotite and vermiculite, the last mentioned presumably an alteration product of biotite. The low plasticity and coherence may be ascribed to the unusually large content of oligoclase in the clay-size fraction, to the sharp-edged irregular shapes of the coarse particles and to the exceptionally well-crystallized character of even the smallest clay particles.