Purple corundum, or sapphire of amethystine tint, is called Oriental amethyst, but this expression is often applied by jewellers to fine examples of the ordinary amethystine quartz, even when not derived from Eastern sources. [Please select]
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As the wheel is of emery, corundum or other quickly cutting material, and is always run at a high rate of speed, a great heat is evolved, which is materially increased by pressure. [Please select]
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This is true whether it has reference to a grindstone, emery, corundum wheel, or a plain oil stone. [Please select]
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