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What else will cut glass?


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Resistance to scratching is known as hardness. Classically it’s measured on a scale of 1-10 with 10 being the hardest. When you rub a hard material against a softer one, the softer will be scratched and the harder will be relatively undamaged. Diamonds are the hardest material in the world and are the definition of a 10 hardness.

Hardness is fairly constant for most minerals. Although there are some slight variations between localities and varieties but it’s very unusual for a variation of more than about 0.1 for a particular stone. Sapphires are always about 9, quartz is always about 6, etc. Glass varies a bit depending on the recipe used by manufacturer but it generally is between 4-5.5. Most natural gemstones are higher than this, most popular substitutes for diamonds are also higher than this and, depending on the pieces of glass used in the test, some glass will be higher others. The end result is that, despite what they say on the television, resistance to scratching isn’t a very good test to identify either diamonds or glass.



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