Those who paid attention to science class may be familiar with the Mohs scale, which measures the relative hardness of a substance. The diamond tops the scale at a solid 10, the hardest substance known to humankind.
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| Image source: nps.gov |
The operant word being “relative.” Anyone under my tutelage would eventually learn that the Mohs scale has its limits. A Mohs hardness is not based on anything quantifiable, instead of being based on comparing how quickly an item is scratched by other minerals or substances.
Hard materials are resistant to abrasion, often being scratched by materials that are even harder. Diamonds earned their ranking by, well, being cut only by their own kind and cutting everything else with almost relative ease. Once sufficiently polished (by another diamond), their facets last forever.
The scale is, from a scientific perspective, imprecise, given the individual variation between mineral samples. More to the point, a mineral’s relative hardness does not mean it is stable. If diamonds were as strong as they were hard, they’d make great building material. Diamonds, however, can shatter. That’s pretty much the only reason why we can even harvest and use them.
The Mohs scale is far from useless. Gem cutters have used this scale to determine how easily a specific gem can be cut to create the desired facets. Stones on the upper end of the scale are usually cut by diamonds, whereas others only need steel knives. Harder gemstones tend to also maintain their luster for years, with diamonds notably maintaining them forever.
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| Image source: intersystek.com |
Rick Casper, diamond gemologist, at your service. Follow me on Twitter more on the science behind gemstones.
