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Article: Top 3 Hardest Gemstones

Top 3 Hardest Gemstones

Top 3 Hardest Gemstones

When selecting gemstones for jewelry or other uses, hardness is one of the most important factors to consider. A gem's ability to resist scratching, abrasion, and everyday wear-and-tear depends greatly on its hardness rating. While beauty, color, and clarity are key, a softer stone may become damaged and lose its luster rather quickly. Understanding gemstone hardness can help you choose more durable stones that maintain their sparkle.

In this article, we'll explore the concept of hardness as it relates to gemstones. We'll look at the Mohs scale of mineral hardness, how it's used to measure gems, and why durability matters. Then we'll countdown and examine the top 3 hardest gemstone varieties. For long-lasting gems that can stand the test of time, hardness is a characteristic that can't be ignored.

Understanding Gemstone Hardness

The Mohs Scale

To understand and compare the hardness of various minerals and gemstones, geologists use the Mohs scale. Developed in 1822 by German geologist Friedrich Mohs, this method ranks minerals on a scale of 1 to 10 based on their relative hardness and resistance to scratching.

Mohs Hardness Scale

Using a set of reference minerals with known hardness values, a gem can be tested by trying to scratch a softer mineral. If it scratches the other mineral, it is rated as harder. The Mohs scale starts with talc at 1, one of the softest minerals, and builds to a maximum of 10 with diamond, the hardest mineral on earth.

Importance of Hardness for Gem Durability

A gemstone's durability and ability to maintain its polish depends heavily on its hardness rating. Harder gems are better able to resist scratches, abrasions, and daily impacts that can damage softer stones. High hardness gives gems like sapphire and ruby their reputation for endurance.

With a lower Mohs rating, gems become more prone to showing wear and scratches, requiring more frequent cleaning and eventual re-polishing. For pieces that will be worn every day, hardness is key for long-lasting beauty and performance. Understanding Mohs ratings helps ensure you select durable stones.

Measuring Gemstone Hardness

While reference minerals help assign an overall Mohs rating, gemologists use specially designed hardness-testing files and tools to get more precise measurements. These devices contain a set of files with increasing hardness grades that can be rubbed across the gem to identify the point scratching begins.

Advanced methods like microindentation can also measure hardness by pressing a diamond-tipped tool into the gem and calculating resistance. These techniques help accurately tier gems that fall between Mohs scale reference points. Most gemological labs provide detailed hardness ratings in their evaluation reports.

Top 3 Hardest Gemstones

Now that we've covered the basics of gemstone hardness, let's countdown the top 3 varieties with the greatest hardness and durability:



Unsurprisingly, diamond tops the rankings as the hardest gemstone, rated 10 out of 10 on the Mohs scale. Diamond's unmatched hardness comes from its tightly bonded crystalline lattice structure, formed entirely out of carbon atoms under immense heat and pressure.

This atomic makeup gives diamond unparalleled strength and resistance to breakage. Diamond's hard, wear-resistant surface also maintains exceptional polish. These factors make diamond the ultimate choice for durable everyday jewelry and the standard for comparison with other gems.

Beyond hardness, diamonds exhibit brilliant refractive properties, dispersing light energy into flashes of fire and brilliance. When expertly cut, diamonds achieve unmatched sparkle and life. Between its hardness and optical performance, diamond remains the most prized of gemstones.



With a Mohs rating of 9.5 out of 10, moissanite has emerged as a rare challenger to diamond's supremacy. Discovered in 1893 by Nobel Prize winner Dr. Henri Moissan, moissanite is made of silicon carbide, found naturally from meteor impacts. Modern moissanite is lab-created for jewelry use.

With hardness surpassing all other gems except diamond, moissanite makes an extremely durable stone able to withstand daily wear. Its crystal structure gives moissanite higher brilliance and fire than almost any gem. Moissanite's affordability compared to diamond has boosted its popularity.

While moissanite looks remarkably similar to diamond, advanced testing can distinguish its subtle differences in hardness, luster, and light transmission. With growing demand, moissanite has proven itself as an innovative alternative for jewelry.



Our third spot goes to corundum, rating 9 out of 10 on Mohs' scale. Corundum is a crystalline form of aluminum oxide notable for its toughness and hardness. Trace elements produce corundum's diverse color varieties including ruby and sapphire.

Only diamond and moissanite exceed corundum's impressive hardness. This makes corundum gems ideal for jewelry exposed to daily wear and tear. Sapphires and rubies are prized for engagement rings and other frequently worn pieces.

Beyond routine use, corundum's hardness adds protection from accidents and impacts that might damage softer gems. Corundum strikes an excellent balance between hardness and affordability, maintaining its status as a top jewelry gemstone.

Factors Influencing Gemstone Hardness

While the Mohs scale gives an overall hardness ranking, other factors can influence a gem's durability:


A gem's toughness, or resistance to chipping, cleaving, and breakage, is also crucial. Toughness depends on a stone's molecular structure and inclusions. Hard gems like emerald are brittle with distinct cleavage planes, making them prone to fracturing if struck. Durability considers both toughness and hardness.


A gem's stability under different conditions affects its hardness retention. Some stones like tanzanite can weaken when heated. Light exposure can fade amethyst. Environmental factors like chemicals, radiation, even pollution can alter gems over time, reducing hardness. Stable gems keep their properties intact.

Setting style

How a gemstone is used in jewelry also impacts its exposure and durability needs. A raised solitaire diamond faces more risk than stones secured in channel settings. Everyday rings and bracelets experience more wear than occasional-use pieces. Settings should match hardness ratings for optimal protection.


When selecting gems for fine jewelry or other uses, hardness stands alongside beauty as a key factor. Understanding the Mohs scale ratings and precisely measuring gemstone hardness helps ensure you choose durable stones that maintain their integrity.

Of all precious and semiprecious gems, diamond, moissanite, and corundum varieties including ruby and sapphire top the rankings as the hardest gems available. Don't let other alluring factors overshadow the importance of hardness. Combine allure with endurance by choosing the hardest gems your budget allows.

Beyond the top contenders, there are many gorgeous gems across the Mohs scale. Always consider a stone's hardness rating for your intended use. With proper care and protective settings, even softer gems can make treasured keepsakes to enjoy for years. Let hardness guide you, then explore the spectrum of gemstone beauty to find your perfect match.