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the edges themselves are not visible, their course is traced out by rows of 
little triangles, all much of a size, in a row. 
On the rotating stage under the microscope the edges of the laminae 
give a singularly pleasing effect. They prove them to be more of the nature 
of steps down facing away from the shorter diagonals of the rhombic faces, 
than of definite protrusions ; and their undeviating straightness, so different 
from the vacillating composition plane of the made, contrasts sharply with the 
rippled surfaces they cut. 
Geometrically, the shorter diagonal of a rhomb of a dodecahedron 
coincides with an edge of the derived tetrahexahedron. The same rule is 
approximately true for such diamonds as are of good symmetry, and are not 
Fig. 3.— Laminated Wesselton diamond, enlarged. 
laminated ; but when diamonds are laminated the rule is varied, in that the 
tetrahexahedron edge tends to slant away from its geometrical position into 
parallelism with the edges of the laminae. This is, perhaps, the most 
important change made by the lamination on the aspect of a stone. 
Fersmann and G-oldschmidt have described (' Der Diamant,' 1911) three 
laminated diamonds, all Brazilian, namely : Crystal No. 26, an irregular 
lump of a weak violet colour, showing lamination in three directions ; 
Crystal 32, a brownish regular dodecahedron, whose surface is covered by a 
delicate network formed of innumerable twin lamellae in four sets ; and 
Crystal 33, a brown dodecahedron with coarse lamination. They argue that 
most diamonds may be presumed to be composed of such lamellae, and that 
the lamination is brought into view by the process of solution. They seem 
further to hold that hemitropic twinning is the cause of the phenomenon. 
