Detecting flaws
An aid to detecting flaws in transparent stones may be furnished by the use of a simple device. If such stones are examined while they are submerged in a colorless liquid of a high refractive index, any flaws which may be present are clearly seen. For this purpose, a glass cell, about six inches long by one inch deep and wide, may be conveniently used. A glass plate, along which a row of holes has been drilled, is placed inside the cell, which should be liquid tight. As the holes are smaller than the stones which are being examined, the latter rest on the surface of the plate. The liquid is then poured over the plate so that the stones are covered. Examination with a microscope will detect flaws fairly easily.
Faults are classified differently by dealers, and the names assigned have only a general significance. Those stones usually classed as V.V.S. are of high quality, showing very slight imperfections detected by an expert with a loupe. Then there is first pique, which is only very slightly spotted, second pique, third pique, slightly imperfect, imperfect, and obvious.
Shades of color also have their various names—blue white (which is very rare), snow white, white, commercial white, silver Cape, Cape, slightly yellow, slightly brown, yellow, brown, etc. It is useful to be able to compare the color of a stone with another which is known, especially in an unfamiliar light. In general, color in a diamond is a greater detraction as far as commercial value is concerned than are internal flaws. When a stone is not white, it is said in the trade to “draw” color.