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Mineral hardness is measured according to how easily a mineral can be scratched. Gemstones such as dia​mond, sapphire, or emerald are very hard (very difficult to be scratched or damaged). The Mohs Scale (developed in 1912 by Friedrich Mohs) identified ten well-known minerals and gave them points on the scale.

Talc is the softest mineral, at point 1. Talc, one form of which is soapstone, can be scratched with a fingernail. In increasing hardness, the next points are labeled with gypsum (2), calcite (3), fluorite (4), apatite (5), orthoclase (6), quartz (7), topaz (8), corundum (9), and diamond (10). Diamond is often used as a cutting tool because of its position as the hardest mineral on the Mohs Scale.

The first nine minerals on the scale have roughly the same spacing between them. For example, topaz is roughly eight times harder than talc. However, diamond is approximately 40 times harder than talc.

Assume that boron (point 9.5 on the Mohs Scale) is halfway between corundum and diamond in hardness. How many times harder than talc is boron?

Steel has a hardness approximately equal to 4.5 points on the Mohs Scale. How many times stronger than steel is a diamond?

Boron hardness relative to talc

Diamond hardness relative to steel







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