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PROPERTIES AND TESTS FOR DIAMONDS
red diamond crystal. In an another case the smaller enclosed crystal was surrounded with another mineral (apophylite).
Some dealers embed large diamonds in raw potatoes to prevent explosion when transported from the mines to England.
One
of the main characteristics of diamond is its hardness. It is the
hardest of all natural things. Some years ago a German mineralogist
named Moh arranged a scale giving the relative hardness of various
minerals, from talc, the softest, to diamond the hardest. He made the
division as follows:
1. Talc, common foliated variety.
2. Gypsum, or rock salt.
3. Calcite, transparent variety.
4. Fluorspar, crystallized variety.
5. Apatite, transparent crystal.
6. Feldspar, cleavage variety.
7. Quartz, transparent variety.
8. Topaz, transparent crystal.
9. Sapphire, cleavage crystal. 10. Diamonds—.
These
minerals were selected because they are constant in the quality of
hardness and reach in steps, from the softest to the hardest; but the
difference of degree between does not correspond with the ratio of the
numbers. The scale therefore does not represent exact and absolute
degrees of hardness, but is an arrangement of minerals of different
degrees in that quality, numbered from convenient reference.
Nor is the diamond always of the same degree of hard-
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