Platinum. This metal is only found native. Its gravity is very high, from 16 to 22. Hardness, 4 to 4.5. Luster, metallic. Opaque. Whitish-gray. Smooth. Ductile. Cleavage, none. Fracture, hackly. Texture, granular, fine. Platinum is unaffected by acids, but if alloyed with 10 per cent. of silver it dissolves in nitric acid. Almost infusible. Platinum occurs with placer gold in the beds of streams. Usually it is in small grains, but one or two large nuggets are on record from Brazil and Siberia. Serpentine rocks are believed to have originally held the platinum found in the beds of rivers, but none has been found in veins. The entire product of the United States was 300 ounces in 1898; valued at $3,837. In 1899 there was none produced. Silver. Silver is generally found in serpentine, trap, sandstone, limestone, shale, or porphyry rocks, the gangue being quartz, calc, fluor, or heavy spar. All silver ores are heavy, and many of them are sectile, i.e., may be cut with the knife. Western men test for silver by heating the ore and dipping it into water. Some metal comes to the surface in a greasy scum, should silver be present. Native silver is found occasionally. Owing to the fall in value of this metal its future is not assured. It has fallen, during the past year, once to forty-nine cents an ounce, and this has had a most disastrous effect upon many silver mines, forcing them to suspend operations. Should the fall continue, as seems likely, and the price of silver go down to forty cents an ounce, little will be produced except as a by-product in the treatment of argentiferous lead ores.