Studies on natural diamonds of the dodecahedral form

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Abstract
Natural diamonds of the dodecahedral form have been studied. Contrary to the widely held belief that the dodecahedral form is derived from the octahedral form by dissolution, it is shown that the process is one of growth. Setting the crystal so that the (110), (101) and (011) faces become equally inclined to the line of the microscope, the three faces could be simultaneously seen and studied. This has led to the discovery that the striatums of dodecahedral faces previously called ‘ruts’(channels) are the spaces between successive layers in the (111) plane, a finding confirmed by the discovery of trigons in the narrow spacings between them. It is shown with examples how straight-edged triangular layers piling up on an octahedral core would produce an ideal sharp-edged dodecahedron and how curved polygonal layers produce the rounded dodecahedron. Boat-shaped features, usually seen on dodecahedral faces, have been shown to be small strips of layers containing trigons. The experimental observation that the dodecahedral face is more easily etched than the octahedral face is explained.

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