Hardness

Hardness describes itself. It is how hard a mineral is. If a mineral can be scratched with yur nail its very soft, if it can be scratched with a penny its slightly harder than if it can be scratched with a your nail. Then it goes up in hardness by what can scratch it, so it goes from lowest to highest with fingernail, a penny, a knife or glass plate, a steel nail, then topaz.

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Wikimedia

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