. Edinburgh journal of natural history and of the physical sciences . The Diasiond—This precious Stone, in its natural state, is of the form of an octahedron. This may be defined a double four-sided pyramid, in which the lateral planes of the one ai-e set on the lateral planes of the other, which will be better understood by the accompanying figure, being a regular octahedron, wherein the triangular faces are equilateral and equiangular, and, of course, the base of the two pvra- mids is a square. Diamonds are always found in detached crystals, and are more or less well shaped, as they are pure
. Edinburgh journal of natural history and of the physical sciences . The Diasiond—This precious Stone, in its natural state, is of the form of an octahedron. This may be defined a double four-sided pyramid, in which the lateral planes of the one ai-e set on the lateral planes of the other, which will be better understood by the accompanying figure, being a regular octahedron, wherein the triangular faces are equilateral and equiangular, and, of course, the base of the two pvra- mids is a square. Diamonds are always found in detached crystals, and are more or less well shaped, as they are pure or otherwise; so that they occur in a variety of forms, of which their primitive one is the basis ; the faces are frequently curvilinear ; they are also subject to the compound crystallization called the made. The structure is perfectly lamellar, yielding readily to mechanical division parallel to all the planes of the regular oc- tahedron, thus proving tliat this is the primitive form. Diamond is the hardest of all substances, and its specific gravity W'hen heated, it becomes phospho- rescent. The general colour of the Diamond is w*hite, but is found of various tints, red like the Ruby, orange like the Hyacinth, blue like the Sapphire, and green hke the Emerald; the last of which is most rare, and of the greatest value when it is of a beautiful tint; the rose, blue, and yellow Diamonds are the next in value. Transparency and brilliancy are the natural and ordinary qualities of the Diamond which exhibits but a single refraction of the rays of hght; some, however, are quite opaque. Diamonds are divided into Oriental and Occidental or BraziUan, the former being the most valuable. Eostius de Boot, in his *' History of Gems," written in 1609, conjectured that the Diamond was inflammable. Mr Boyle discovered, in 1673, that when exposed to a high temperature, it gave out acrid vapours, in which a pan of it w*as dissipated. Sir Isaac Newton, who composed his work on Optic
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