Tools for asaying gold and silver, 1574-1679.
© Science Museum / Science & Society Picture Library
Touchstones are black, silica-containing stones that were first mentioned by Theophrastus (372-287 BC) in his treatise 'On Stones' and are still in use today as a quick method of making an approximate estimate of the proportion of gold or silver in a sample of metal. The touchstone and needles shown here were made up according to instructions given in Lazarus Ercker's 'Treatise on Ores and Asaying' published in Prague in 1574. They lie on an open page of 'A New Touchstone for Gold and Silver Wares', a small treatise on asaying published in 1679 explaining the law relating to gold and silver.