Statistical Distribution Patterns of Particle Size and Shape in the Georgia Kaolins

Abstract

Abstract H igh resolution electron micrographic techniques have been employed for surveying the size and shape distributions of kaolinite particles, both plates and stacks, from well-crystallized Georgia deposits. Both size and shape follow typical, positively-skewed, frequency distributions. Particle thicknesses among plates appear quantized, dominantly as hoxalaminae and subordinately as trilaminae of the basic c -axis dimension in the unit cell. Specimens subjected to severe shear and attrition show intermediate values of thickness, i.e. 3 n + 1 and 3 n + 2. Profile studies on kaolinite stacks reval integral platelet units whose distribution in thickness corresponds to that of individual plates. Energy calculations for fracture (cleavage ‖ to c -axis) and delamination (cleavage ⊥ c -axis) processes indicate that hydrokinetic cleavage in nature should result in particles having an aspect ratio distribution peaking near 6: 1. The dominance of stacks above 10 μ is suggestive of in situ weathering. Experimental shear measurements correlate well with these proposals. Sedimentation studies with clays of various shapes and distributions were performed in a variety of aqueous media, including sea water. Sediment volume data, microscopic observations, and theoretical packing calculations are compared with the several mechanisms proposed for plate-stack genesis.