The Diamond Crystal

The diamond is the hardest and one of the most valuable of gems, the purest form in which the element carbon is found. In crystallizes in forms belonging to the regular, or cubic, system, the most common being the regular octahedron and the rhombic dodecahedron (twelve faces). The finest diamonds are colorless, perfectly clear and transparent. Such are said to be the first water. But diamonds are often blue, pink, green or yellow, and such are highly prized, if of a decided and equal tint throughout. The diamond is so very hard that nothing will scratch it - it is, in fact, the hardest substance known.

The value of a diamond is much enhanced by the cutting of facets upon it, inclined at certain angles to one another, so as to produce the greatest possible play of color and luster. What is called the brilliant cut best brings out the beauty of the stone. Its upper or principal face is octagonal, surrounded by many facets. But this form of cutting requires an originally well-shaped stone. For other diamonds the rose cut is used. In this form six triangles are cut on top so that their apices meet in a point called the summit. Round this are disposed other facets. Stones which are too thin to cut as rose diamonds are cut as table diamonds, which have a very slight play of color. The art of cutting and polishing the diamond was unknown in Europe till the fifteenth century, and the stone itself was not nearly so highly valued in the Middle Ages as the Ruby.