Ten Hardest Gems & Minerals

One of the methods used to measure mineral hardness, and one that is regularly used to classify gems and minerals, is the Mohs Scale. Created by Friedrich Mohs, a German geologist and mineralogist, in 1812, the Mohs Scale ranks minerals based on their scratch resistance. The more minerals that can scratch the tested mineral, the lower its number on the Mohs Scale. Conversely, harder minerals will scratch softer ones. It's common for people to confuse gemstones with minerals, but the Mohs Scale helps clarify their differences. For instance, diamonds, sapphires, and rubies are among the hardest minerals and are highly valued as gemstones. Below, I will discuss the hardest gems and minerals found on the planet, according to the Mohs Scale. For more detailed information, you can also read our article on the differences between gemstones, rocks, and minerals

1. Diamond: 10

Diamonds are loved for many reasons, including their resistance to wear and tear. As the hardest mineral found on earth, diamonds are the least likely to change with time. They form under incredibly high pressure, way beneath the Earth's surface - hundreds of miles beneath the surface, in fact!

2. Boron: 9.5

This chemical element is produced by something called cosmic ray spallation, which is a type of nuclear fission that occurs naturally. Its naturally occurring compounds are more common than boron in its purest form. Boron compounds are used for a variety of purposes, including in fiberglass insulation, bleaches, and silica-based glasses to provide thermal shock resistance.

3. Stishovite: 9.5

Very hard and very dense, stishovite was first synthesized by Russian physicist Sergey M. Stishov in 1961 and was found in a meteorite impact site by Edward C.T. Chao in 1962. Through the application of hydrogen fluoride, stishovite can be separated from quartz.

4. Moissanite: 9.25

Thanks to its rarity, moissanite wasn't introduced to the jewelry market until 1998. It's very comparable to diamonds but with a lower price, and it's therefore often sought as a diamond alternative.

5. Titanium Carbide: 9-9.5

Very resistant to corrosion, wear, and oxidation, titanium carbide is often used to coat watches, in tool bits, and sometimes as a heat shield for spacecraft to allow for atmospheric re-entry.

6. Corundum: 9

A naturally clear transparent rock-forming mineral, corundum is a form of aluminum oxide with traces of titanium, chromium, and iron. Because of how hard it is, it is able to scratch almost all other minerals. It is used commonly as an abrasive.

7. Tungsten Carbide: 9

Very hard, tungsten carbide is used for a variety of purposes, including jewelry. When used in jewelry, it is often incorrectly simply called tungsten, even though tungsten carbide actually consists of equal parts tungsten and carbon. It has become as popular as it is in the jewelry industry due to its resistance to scratching and extreme hardness.

8. Chrysoberyl: 8.5

This natural gemstone is interesting because of its cyclic twins called trillings. The twinned crystals look sort of hexagonal in appearance and are usually greenish-yellow in color, though various shades of green, brown, yellow, and other colors exist.

9. Cubic Zirconia: 8.5

The first discovery of a naturally occurring cubic zirconia was made in 1937 by German mineralogists K. Chudoba and M.V. Stackelberg. They found it within metamict zircon in the form of microscopic grains and did not think it important enough to name at the time. Today, cubic zirconia is mass produced in the jewelry marketplace. Because cubic zirconia so rarely occurs naturally, the cubic zirconia found in jewelry is created or synthesized by humans.

10. Chromium: 8.5

Not only is chromium very hard, but it also has a very high melting point. It is brittle and lustrous, taking a high polish and able to resist tarnishing. It was first used during the Qin dynasty over 2,000 years ago by the Chinese as a coating for the metal weapons that were found with the Terracotta Army.

I hope you found this as interesting as I did! I'm finding that the more I learn about minerals and gems, the more I feel the need to research. Let me know if you have anything to add! I'd love to read any interesting facts you want to share.