In Mr. Milburn's valuable work on Oriental Commerce, he gives some very interesting observations on the peculiar characteristics of rough diamonds. According to this writer, the color should be perfectly crystalline, resembling a drop of clear spring water, in the middle of which will be perceived a strong light, playing with a great deal of spirit. If the coat be smooth and bright, with a little tincture of green in it, it is not the worse, and seldom proves bad ; but if there is a mixture of yellow with green, it is a soft, greasy stone, and will prove bad. If the stone has a rough coat, so that the eye can hardly penetrate it, and the coat be white, and look as if it were rough by art, and clear of flaws or veins, and no blemish exist in the body of the stone—which may be discovered by holding it against the light—the stone will prove good. If a diamond appears of a greenish bright coat, resembling a piece of green glass, inclining to black, it generally proves hard, and seldom bad ; such stones have been known to have been of the first water, and seldom worse than the second ; but if any tincture of yellow seems to be mixed with it, it may be regarded as a very poor stone. All stones of a milky cast, whether the coat be bright or dull, if ever so little inclining to a bluish cast, are naturally soft, and in danger of being flawed in the cutting ; they will prove dead and milky, and turn to no account. All diamonds of cinnamon color are dubious. A good diamond should never contain small spots of a white or grey color, of a nebulous form. It should also split readily in the direction of the cleavage ; it sometimes happens, however, that the folia are curved, as is the case in twin crystals. When this happens, the stone is of inferior value.—Philadelphia North American