a certain type of flint-like rock gold prospectors would carry to scratch their gold against to make sure it was real gold
a criterion, a metric of the value of something
a criterion (used in the Renaissance as a test for the purity of gold and silver)
a device for roughly ascertaining the purity of gold alloys
a hard black stone that's used for testing the purity of precious metals
a rock on which a piece of gold or silver is rubbed
a small tablet of dark stone such as fieldstone or slate , used for probing of precious metal alloys
slightly rough, black stone usually made from quartz, jasper, or slate, which would be rubbed with a sample of ore. Assayers would use touch needles to examine the composition of the ore
The black stone upon which metals were rubbed to give a streak of characteristic color indicating the type and quality of the metal.
A heavy black stone, usually jasper or basalt, used to test the quality of gold or silver.