Assertion: alumina's hardness | /r/HasAspect | high melting point of 2,045 °c
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Source sentences:
text: Its crystalline form, corundum, is very hard (Mohs hardness 9), has a high melting point of 2,045 °C (3,713 °F), has very low volatility, is chemically inert, and a good electrical insulator, it is often used in abrasives (such as toothpaste), as a refractory material, and in cermanics, as well as being the starting material for the electrolytic production of aluminium metal.