This listing is for a Small Touchstone for Testing Precious Metals. This test stone measures 2" x 1-1/2" x 3/8". Each order is for one test stone, test solutions must be purchased separately. This item is new from our inventory.
A touchstone, also refered to as a test stone, is a small, abrasive, silicone based stone that is impervious to acid and easy to clean. When a metal is rubbed on a touchstone, a small amount of the metal is deposited on the stone, forming a colored stripe. This is usually compared to a strip ground from a known metal. A drop of testing solution is then applied to the stripes. By observing the reaction between the acid and the metal stripes, the purity of the metal can be determined.