. Precious stones, a popular account of their characters, occurrence and applications, with an introduction to their determination, for mineralogists, lapidaries, jewellers, etc. With an appendix on pearls and coral. Precious stones; Pearls; Corals. DIAMOND: CRYSTALLINE FORM 121 peculiarities, however, render the hemihedrism of the crystals open to question, and some authorities prefer to consider them as holohedral. All the typical simple forms of the cubic system have been observed in diamond crystals, either alone or in combination with other. Fig. 31, li-s. Crystalline forms of diamond. fo
. Precious stones, a popular account of their characters, occurrence and applications, with an introduction to their determination, for mineralogists, lapidaries, jewellers, etc. With an appendix on pearls and coral. Precious stones; Pearls; Corals. DIAMOND: CRYSTALLINE FORM 121 peculiarities, however, render the hemihedrism of the crystals open to question, and some authorities prefer to consider them as holohedral. All the typical simple forms of the cubic system have been observed in diamond crystals, either alone or in combination with other. Fig. 31, li-s. Crystalline forms of diamond. forms. Some of the more commonly occurring forms, which will be described in some detail, are shown in Fig. 31, o-jo. Crystals having the form of a regular cube (Fig. 31 a) occur very frequently, but are usually small; this habit is specially characteristic of Brazilian crystals, and is rarely met with in specimens from other localities, especially the Cape. The faces of the cube are always dull and rough, and show a shallow depression, increasing in depth towards the centre of the face. The roughness is due to the presence of square-based, pyramidal depressions placed diagonally on the cube face; these are usually small, but may be of fair size. They occur more or less isolated or closely aggregated together (Fig. 31 a). When observed with a lens or, better still, under the microscope, the pyramidal faces bounding the shallow depressions may be distinctly seen; they are marvellously plane and smooth, but just as frequently rough and irregular, and between these two extremes all. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bauer, Max, 1844-1917; Spencer, Leonard James, 1870- tr. London, C. Griffin and Company, Ltd.
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