The diamond fields in India are very extensive, and occur everywhere among the hills of the great range that extends from Cape Comorin through the whole of Bengal for a distance of several hundred miles and with an average breadth of fifty miles. How long these mines have been known to man must always remain a matter of conjecture; but it is nevertheless certain that the famous mines have been discovered within the past thousand years, and probably a much less period of time. It is stated that many of the gem districts along this range have not been explored carefully, and that the kingdoms of Golconda and Visapour alone have supplied most of the gems known in India. And it is also related that none of these localities have been scientifically mined or surveyed with a view to thorough development. The most ancient of the diamond mines in India are supposed to be those of Soumelpour, near the river Gonet, a tributary of the Ganges; but the celebrated mines of Golconda and Raolconda have been known only since the fifteenth and sixteenth centuries. The richest mine of India, and the most extraordinary of any yet discovered in the world, is that known by the name of Gani, or Couleur. It is situated under a plain at the foot of a mountain about seven days’ journey west of Golconda, and was discovered by accident about the middle of the sixteenth century. A native digging the earth to sow millet threw up a bright, clear crystal of twenty-five karats. It was soon recognized to be a diamond, and crowds of Hindoos flocked to the fields to reap the most wonderful harvest of gems yet known. A vast number of large gems were obtained, and among them the Great Mogul, which weighed in its rough condition seven hundred and ninety-three karats. The gems of this mine were remarkable for their large size, but they were not of the clearest and purest water, the color and lustre of the stone seeming to partake of the quality of the earth composing the matrix. This idea, which prevails among the miners in other gem districts in India and also in other countries, lends support to the belief that the diamonds were formed in the strata of gravel where they are now found, and not in the hard crystalline rocks and afterwards set free by disintegration. The matrix of these mines, as well as of all the others in different parts of the world, is essentially the same; and consists of rolled or broken masses of quartz, mixed or united with sand or earth impregnated with a ferruginous oxide. Amongst this conglomerate, or immediately below it, mixed with clay, the diamonds are found, and generally unattached to any substance.