Cornish DIAMOND, a name given by many to the rock crystals found in the mines of tin in Cornwall. These crystals are usually bright and clear, and are found most frequently in the form of an hexangular column terminated at each end by an hexangular pyramid.
Rose DIAMOND is one that is quite flat underneath, with its upper part cut in divers little faces, usually triangles, the uppermost of which terminate in a point. In rose diamonds, the depth of the stone from the base to the point must be half the breadth of the diameter of the base of the stone. The diameter of the crown must be of the diameter of the base. The perpendicular, from the base to the crown, must be of the diameter of the stone. The lozenges which appear in all circular rose diamonds, will be equally divided by the ribs that form the crown; and the upper angles or facets will terminate in the extreme point of the stone, and the lower in the base or girdle.