What is the Mohs Scale of Mineral Hardness and Why You Should Care About It

by Carly Wickell

What is the Mohs Scale?

In the early 1800s, Frederick Mohs developed a chart that compared the hardness of ten easily accessible minerals, beginning with talc (at the softest rating, 1) and working up to diamond (with a rating of 10, the hardest). The chart is known as the Mohs scale and is still used today.
Rankings are a comparison of hardness among ten minerals. Those with higher numbers will scratch minerals with lower numbers, but aren’t necessarily close to each other in hardness. For instance, diamond (10) will scratch corundum (9), but is actually four times harder.

Expanded rankings of minerals and materials offers an overview of their durability as it relates to hardness.

Original Mohs Scale
Talc
Gypsum
Calcite
Fluorite
Apatite
Feldspar
Quartz
Topaz
Corundum (ruby, sapphire)
Diamond

Relative Hardness of Other Materials
Pearl: 2.5
Fingernail: 2.5
Gold: 2.5 to 3
Coral: 3-4
Platinum: 4 to 4.5
Tooth: 5
Opal: 5.5
Lapis: 5-6
Turquoise: 5-6
Glass: 6-7
Periodot: 6.5-7]
Quartz: 7
Garnet: 7 to 7.5
Emerald: 7.5-8
Topaz: 8

Why Should You Care About the Mohs Scale?
Jewelry Storage: Sapphire scratches opal (and anything else rated below 9) and should not be stored in a location where the two can bump up against each other.

Everyday Wear: At 2.5, pearls would suffer from the wear and tear of everyday use and should be worn with care. Diamonds, at a hard 10, are a good choice for engagement rings, and so are 9-rated ruby and sapphire.
Hardness isn’t the only factor to consider when you buy a gemstone, but it’s an important ingredient for determining durability.

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