WEIGHT. The valuable precious stones are bought and sold by the carat. This weight is equal to about 3.17 grains or about .205 milligrams. The carat is divided into fractions of ½, ¼, ⅛, 1/16, 1/32, 1/64, and also arbitrarily into four grains; that is, each quarter of a carat is counted one grain, thus forming the basis for the calculation of pearls. In commerce, a carat diamond is sometimes called a four-grain stone, and a carat-and-a-half stone is six grains, etc., etc. The weight of the carat being arbitrary, it varies in different countries, some being heavier and others lighter than .205 milligrams. The writer wrote to three prominent balance-makers in the United States some months ago for their carat standards and was surprised to find that they all differed. This will account for discrepancies in weight resulting between the balances of different makers. Of late there has been a decided movement in Europe, headed by the French Chambre Syndicale of jewelers, in favor of the unification of the carat, so that the weight of a French or Dutch carat will equal that of an English, American, or any other carat. This reform will probably be accompanied by the adoption of the decimal system of dividing the carat, and the discarding of the complicated fractional system. After having tried the decimal weights for many months, the author can testify to a decided gain in time and accuracy from their use. FUSIBILITY. The blow-pipe or dry test for minerals is convenient to apply to small bits or splinters of a stone. The mineral is either held by a pair of platina-pointed forceps, or powdered and placed on a metal plate or in a glass tube. Before the blow-pipe, some minerals change color, but do not melt, while others retain their color, or swell up, or break into small particles, or melt into colorless or colored glasses. The following is the scale of minerals used to test the different degrees of fusibility: 1. Gray Antimony. Fusible in coarse splinters in summit of candle flame without the blow-pipe. 2. Natrolite. Fusible in fine splinters in the summit of a candle flame without the blow-pipe. 3. Almandite. Does not fuse in candle flame; fuses easily before the blow-pipe in obtuse pieces. 4. Green Actinolite. Fusible before the blow-pipe in coarse splinters. 5. Orthoclase. Fusible before the blow-pipe in fine splinters. 6. Bronzite. Before the blow-pipe becomes rounded only on the sharp edges. MAGNETISM. There are but few precious stones that possess the power to act on the magnetic needle; among them are the chrysolite, cinnamon stone, almandine, pyrope, and garnet. TRANSPARENCY.