Five siliceous pebbles suitable for use in assaying gold, Oman, 1994

Made:
1994 in Oman
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 

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

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

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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 pebbles from various locations, selected for their suitability for gold assaying purposes when used as touchstones: Five black pebbles collected on the beach at Medinat Qaboos, Muscat, Oman, in February 1994. Marked 1994-3

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:
2019-91
Materials:
stone
type:
touchstones
credit:
Gift of Dr W.A. Oddy