Traditionally a piece of polished black siliceous rock, treated with nitric acid, was used to identify minerals from the quality of the powder left behind by a stone.
The modern standard is white unglazed porcelain of the same hardness as quartz. Traditionally a piece of polished black siliceous rock, treated with nitric acid, was used to identify minerals from the quality of the powder left behind by a stone. For 10 points—name this tool used by mineralogists to determine the quality of gold.
The modern standard is white unglazed porcelain of the same hardness as quartz.
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