touchstone
Sign in to savesmall tablet of dark stone used for assaying precious metal alloys
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Touchstone set
A touchstone is a small tablet of dark stone such as slate or lydite, used for assaying precious metal alloys. It has a finely grained surface on which soft metals leave a visible trace. Basic requirements for a touchstone: hardness on the mineralogical scale 4.6-6.5, the touchstone must be free of cracks and not react with inorganic acids and their mixtures.
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gold
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metal
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Ancient Greece
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International Standard Book Number
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alloy
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Indus Valley Civilization
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digital object identifier
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International Standard Serial Number
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nitric acid
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aqua regia
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bibcode
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litmus
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open access
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slate
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streak
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precious metal
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fineness
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radiolarite
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Metallurgical assay
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Touchstone
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