Lydian touchstone
The Lydian touchstone is a fine-grained black Lydian that has proven itself to be the best material because it possesses all the characteristics required of a good testing stone. It must be uniformly matte black, has a homogeneous, non-porous structure and is harder than the metals being tested, it is resistant to acids and the stone may not be worse of quality after a few cleanings. Despite many years of attempts, it has not yet proven to develop an artificial material with these ideal characteristics.
Our touchstones are in various sizes, and so also in weight, this is because only the best part of the original rough stone can be used. The stones become, after sawing, a long-standing polish process. After polish the stone will be totally checked at imperfection so that finally every stone has the same quality.
The historie:
The touchstone was the first method of assaying gold and was used at least as early as 500 BC, the earliest touchstones long strips of slate having been found in excavations at the ancient city of Taxila in Pakistan with traces of gold streaks still on their surface. Touchstones are still widely used, particularly in the bazaars of India, jewellery and in assay offices around the world.