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What is the Mohs Hardness Scale?

What is the Mohs Hardness Scale?

What is the Mohs Hardness Scale?

In the world of diamonds and precious gemstones, understanding the physical properties of these valuable stones is essential. One of the most crucial aspects of identifying and classifying minerals is their hardness. How do gemologists measure this property accurately?

The Mohs Hardness Scale is a simple and clever way to study diamonds and gemstones that has been used for centuries. Let’s explore where the Mohs Hardness Scale came from, why the scale is necessary, and how it works. Learning more about the Mohs Hardness Scale will help anyone searching for the right piece of diamond and gemstone jewelry.

The Mohs Hardness Scale: A Brief History

Image of Freidrich Moh

So, let's first begin by addressing the question, "Why is it called the Mohs Scale?"

The Mohs Hardness Scale is named after the German mineralogist Friedrich Mohs, who introduced the concept in 1812. The tool takes a qualitative approach and determines the relative hardness of minerals.

However, unlike other quantitative methods that require sophisticated laboratory equipment, the Mohs Scale relies on the practicality of scratching one Mineral against another. Since minerals are the building blocks of the Earth itself, they hold invaluable clues about the planet's geological history. Therefore, mastering the Mohs Hardness Scale is an indispensable skill for professionals, including geologists, archaeologists, jewelers, and anyone curious about and exploring the natural world.

How is the Mohs Scale of Hardness Used in the Jewelry Industry?

Mohs Hardness use in the Jewelry Industry

The Mohs Hardness Test is important in jewelry. It empowers gemologists to check how durable gemstones are, like lab-grown diamonds. It shows how well gemstones can withstand wear and tear.

For some clarity, the Mohs Hardness Scale ranges in numbers from one to 10. It assigns a hardness value to diamonds and gemstones based on their ability to be scratched by other minerals.

For instance, at the very bottom of the scale is talc. This incredibly soft Mineral is easily scratched – you could scratch it with your own fingernail! At the same time, at the top of the scale sits the diamond, the hardest known Mineral on Earth, which can also scratch all other substances. Ultimately, the simplicity of the Mohs Scale makes it a precious tool in the jewelry world — and aids in the overall selection, setting, and care of diamonds and gemstones.

Remember these points for better understanding when learning about the Mohs Hardness Scale in the diamond and gemstone trade.


  • Gemstone & Diamond Selection: Choosing the right gemstone or lab-grown diamond is paramount when crafting jewelry. The Mohs Hardness Scale empowers jewelers in this process by indicating a stone's resistance to scratches and abrasions.

  • Gem Quality: Colored gemstones with higher hardness values, such as a blue sapphire or a red ruby, are often preferred for rings and other jewelry items worn daily as they are less likely to be damaged by everyday wear and tear. Conversely, softer stones like opals and pearls are usually set in earrings and pendants, where they are less susceptible to impact and scratches.

  • Setting Techniques: A jeweler or gemologist will use the Mohs Hardness Test to determine suitable settings for diamonds and gemstones. Stones with higher hardness, such as a lab-grown diamond, can withstand secure settings that grip them firmly — this ensures the piece's longevity and prevents accidental damage. For delicate gems, a jeweler may choose a setting that provides extra protection, like a bezel or halo design. These settings encircle the gemstone entirely, safeguarding it from potential damage.

  • Care & Maintenance: Finally, knowing the hardness of a gemstone is vital when a jeweler or gemologist educates their customers on proper care and maintenance. By understanding a stone's position on the Mohs Hardness Scale, a jewelry consumer can avoid wearing the piece during any activity that might harm the ring, necklace, or bracelet. For instance, wearing a ring with a softer stone when doing physical work could result in scratches and chips. Educated consumers are also empowered to appreciate their jewelry while taking appropriate precautions, which will preserve the beauty and integrity of their diamond or gemstone for the long term.


The Mohs Hardness Scale is an imperative guide in the ever-evolving world of jewelry design and craftsmanship. This grading system is something we pay close attention to at MiaDonna with every piece of lab-created gemstone jewelry we promote and showcase.

The Mohs Scale of Hardness — Breaking Down from One to 10

Mohs hardness scale from 1-10

As we noted, understanding the durability and toughness of minerals is paramount. The Mohs Hardness Scale has been the gold standard for identifying minerals for over 200 years. From the softest talc to the most intricate diamond, this scale quantifies the resistance of minerals to scratching, providing an essential framework for scientists and jewelers… not to mention jewelry shoppers.


Here is a deeper look at the Mohs Scale of Hardness Chart:

  1. Talc: Talc is the softest Mineral on the Mohs Scale. It is so weak that a fingernail can scratch it.

  2. Gypsum: Slightly stronger than talc, gypsum is still very soft. This substance is used in the creation of plaster and chalk.

  3. Calcite: Calcite is a relatively soft mineral that a copper coin or knife blade can scratch.

  4. Fluorite: Fluorite is a colorful mineral that is slightly harder than calcite. However, it can still be scratched by everyday objects.

  5. Apatite: Harder than fluorite, apatite can only be scratched by a knife blade or other minerals that sit higher on the Mohs Scale.

  6. Orthoclase Feldspar: This is a common mineral found in many rocks. Orthoclase feldspar is hard enough to scratch a glass surface.

  7. Quartz: A widely distributed mineral, quartz is significantly more complex than most common minerals. It can scratch glass and is used in jewelry making.

  8. Topaz: Recognized as a complex and durable mineral, topaz is also commonly used in jewelry-making processes. It is more complicated than quartz and can only be scratched by corundum or diamond.

  9. Corundum: This Mineral includes precious gemstones such as ruby and sapphire. It is a tricky substance and can scratch most other minerals.

  10. Diamond: Diamond is the hardest Mineral on the Mohs Scale – even harder than corundum – and experts recognize it as the hardest Mineral on the planet. Diamonds are exceptionally tough and can only be scratched by another diamond. This incredible hardness is one of the reasons why diamonds are highly prized in the jewelry industry. Plus, this designation encompasses not only natural diamonds but also lab-grown diamonds. Any cut diamond of any carat weight will register as a 10 on the Mohs.


As you can see, the Mohs Scale is quite simple and very easy to use since it does not require any advanced lab equipment. Today, it is used in many fields of study and industry.

How is the Mohs Scale used with lab-grown diamonds?

The Mohs Scale indirectly influences the diamond industry, so examining how this hardness test is used in lab-grown diamonds is worth reading. The Mohs Scale of Hardness is not used to grade lab-grown diamonds. Other methods and scales are used to evaluate the quality and characteristics of diamonds, whether lab-grown or earth-mined.

Lab-grown and natural diamonds both rank ten on the Mohs Scale for hardness because they are physically, chemically, and optically identical to each other.

Identifying a lab-grown diamond from an earth-mined diamond involves other tests and techniques performed by gemologists and specialized laboratories. These methods aim to detect the unique features and characteristics specific to lab-grown diamonds. Here are some standard tests used for this purpose:

  • Microscopic Inspection: A gemologist will use microscopes to examine the internal features of diamonds. Specific growth patterns, inclusions, and other characteristics visible under high magnification can explain the diamond's origin.

  • Laser Inscription: Many lab-grown diamonds are laser-inscribed with a microscopic serial number or logo. While not visible to the naked eye, this inscription can be used to trace the diamond's origin back to the lab where it was created.

  • Ultraviolet (UV) Light Testing: A diamond can exhibit fluorescence under UV light. While natural and lab-grown diamonds can both fluoresce, the specific fluorescence patterns can sometimes differ, providing hints about the stone's origin.

  • Spectroscopy (UV-visible and Infrared Spectroscopy): Spectroscopic analysis measures how a diamond interacts with light. Natural and lab-grown diamonds can have different UV, visible, and infrared absorption spectra.

  • Raman Spectroscopy: This method is used to analyze the diamond's crystal structure, and earth-mined and lab-grown diamonds can have distinct Raman spectra due to differences in their growth environments.

  • Advanced Imaging Techniques: Other technologies, such as scanning electron microscopy (SEM) and photoluminescence (PL) mapping, provide visualizations of a diamond's internal and surface features, aiding in the differentiation process.


Their many tools are used in the diamond industry regarding natural and lab-grown diamonds. Of course, the Mohs Scale of Hardness is also valuable in determining if a diamond is a diamond or some other mineral with less hardness.

Mohs Scale of Hardness FAQs

Why is the Mohs Scale Important?

Simply put, it provides a practical way to compare the hardness of different minerals. It enables scientists, geologists, jewelers, and engineers to understand the physical properties of minerals, aiding in mineral identification, gemstone selection, and evaluating materials used in varied industries.

What Mineral is Ten on the Mohs Scale?

Diamond is ranked tenth on the Mohs Scale, making it the most complex Mineral due to its unique crystal structure and atomic solid bonding. Its hardness makes it capable of scratching all other minerals.

Where is Emerald on the Mohs Scale?

Emerald is a variety of the mineral beryl and is typically found with a hardness ranging from 7.5 to 8 on the Mohs Scale. It is relatively complex but can still be scratched by more complex minerals such as corundum (ruby and sapphire) and diamond. Despite its vibrant beauty, emerald is easier than other gemstones. It requires careful handling and protection to prevent scratches and damage.

Which Precious Gemstone Scores Lowest on the Mohs Scale?

The answer to this is opal, as it has a relatively low hardness that ranges from 5.5 to 6 on the Mohs Scale. This makes opal softer than many other popular gemstones, including quartz, sapphire, and diamond.

As such, opals are more susceptible to scratching and abrasion. They require special care and are often set in protective jewelry settings to minimize the risk of damage. However, opals are still treasured for their mesmerizing colors, making them highly prized in the world of gemstones.

Where Does Moissanite Rank on the Mohs Scale?

Moissanite, a naturally occurring mineral often mistaken for a diamond, ranks 9.25 on the Mohs Scale. Moissanite is popularly synthesized as a gemstone due to its brilliance, durability, and close resemblance to diamonds. Additionally, moissanite is highly resistant to scratching and wear, making it an excellent choice for jewelry.

How Can I Know I’m Buying a Good Diamond?

Aside from the Mohs Scale, it’s important to consider the 4 C’s of diamonds: cut, clarity, carat weight, and color. Our non-commissioned diamond experts are happy to answer any questions you have about how to choose the right diamond for your budget. MiaDonna is also proud to provide diamond grading reports for every diamond we sell, from the jewelry industry’s most trusted third-party verification agencies, the International Gemological Institute (IGI) and Gem Certification & Assurance Lab (GCAL).

MiaDonna Specializes in Lab Grown Diamonds & Gemstones

At MiaDonna, we care about giving customers top-quality lab-grown diamonds and gemstones. We think well-informed shoppers will be happy and confident with their jewelry purchases.

Please get in touch with us with any questions about selecting lab-grown diamonds or gemstones for your jewelry. We are happy to help you one-on-one as your personal buying guide. We can answer any questions you have about diamonds, in-person at our Portland store, or online at a Virtual Appointment anywhere in the world!

Reach out to our team today. We would love to be your partner to ensure you have a piece of jewelry you will value for years.


MiaDonna Team

MiaDonna is the world’s first retailer exclusively selling Lab-Grown Diamonds and Gemstones, created in 2005 by a mother determined to free families from a lifetime of poverty and mining. We specialize in designer-style fine jewelry that is beautiful, sustainable, and affordable. We are B-Corp certified, environmentally responsible, and donate 10% of profits to support communities negatively impacted by diamond and gold mining. MiaDonna is headquartered in Portland, Oregon and ships to all 50 states plus more than 30 countries internationally.