Touchstone testing is mainly used for checking and hallmarking precious metal articles. It is done directly on the object. The touchstone is a hard natural or artificial stone with a matte surface. The unknown is rubbed with the touchstone to produce a powder of the metal on the surface. This area of rubbings can be compared in appearance to standard alloys similarly treated, or tests can be done on the area with various reagents. Tests for gold and silver alloys can be made, and differentiation between platinum, white gold, palladium, and stainless steel is possible. Extensively illustrated in color.