Stone samples suitable for use as touchstones for assaying gold, Czech Republic

Made:
1978-1995 in Czech Republic
Several samples of natural black pebbles from various locations Several samples of natural black pebbles from various locations Several samples of natural black pebbles from various locations

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Creative Commons LicenseThis image is released under a CC BY-NC-SA 4.0 Licence

Buy this image as a print 

Buy

License this image for commercial use at Science and Society Picture Library

License

Creative Commons LicenseThis image is released under a CC BY-NC-SA 4.0 Licence

Buy this image as a print 

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License this image for commercial use at Science and Society Picture Library

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Several samples of natural black pebbles from various locations
Science Museum Group
© The Board of Trustees of the Science Museum

Several samples of natural black pebbles from various locations
Science Museum Group
© The Board of Trustees of the Science Museum

Several samples of natural black pebbles from various locations
Science Museum Group
© The Board of Trustees of the Science Museum

Several samples of natural black stones from various locations, selected for their suitability for gold assaying purposes when used as touchstones: Four samples of ‘Lydian stone’ or ‘basanite’ from a source near Prague, Czechoslovakia, together with a replica of a medieval touchstone (marked 1978-2) made from this basanite. There are modern gold streaks on the surface.

Touchstones are fine-grained siliceous stones, on whose abrasive surface a gold sample undergoing checks for purity would be rubbed. A streak of gold would be left on the stone’s surface, which could be compared against gold of known quality, to establish the sample’s purity. Touchstones were the main means of assaying the quality of gold throughout history, but remain in use today.

Details

Category:
Metallurgy
Object Number:
2019-94
Materials:
stone
type:
stone samples
credit:
Gift of Dr W.A. Oddy