How Hard Is Your ROCK?
Aquamarine that was worn hard for over 20 years.
Understanding the Mohs Scale & Choosing Durable Stones
When you shop for stones, you are probably considering color, pattern, sparkle, uniqueness, symbolism or maybe event the metaphysical properties. But you should also be thinking about hardness.
Hardness is a measurement of how well a material resists scratching. In other words, it tells you how easily a surface can be scuffed, abraded, or worn down over time. That’s why it’s so important to understand the Mohs Scale of Hardness when you’re working with different rocks.
What is the Mohs Scale?
Developed in 1812 by German geologist Friedrich Mohs, the Mohs Scale ranks materials on a relative scale from 1 (softest) to 10 (hardest). It's based on the principle that a harder material can scratch a softer one. This scale helps us identify what can and can’t scratch a particular stone or material.
Let’s do an example:
Pyrite - Photo by Caleb Jack on Unsplash
Say I want to make a ring with a pyrite stone.
Pyrite has a Mohs hardness of 6–6.5. With that hardness, I can safely set the stone using a brass bezel pusher (hardness ~3) without worrying about scratching the surface during setting.
However, if I do any cleanup with a file, graver, or use one of those silly hardened steel bezel pushers, I need to be extra careful. Hardened steel has a Mohs hardness around 7–8, which means one slip with too much pressure and and I can scratch the pyrite.
Once the ring is out in the world, it will come into contact with all kinds of materials, but the most common will be quartz, Since quartz has a Mohs hardness of 7, it’s harder than pyrite. Over time, consistent exposure to quartz particles will gradually abrade the surface of the pyrite, eventually showing fine scratches and signs of wear.
Pick a 7+
Why is Quartz so important? Fun fact: It is the most abundant mineral on Earth’s surface, forming sand, silt, and countless rocks. This means that when your finished piece of jewelry is worn and comes into contact with dust, countertops, or even your clothing, it’s essentially getting rubbed by microscopic quartz grains.
If your stone is softer than quartz, aka the world, it’s much more likely to accumulate scratches over time. That’s why stones that are intended for regular wear (especially rings or bracelets!!) benefit from being rated a 7 or higher—they hold up far better.
Some stones Rated 7+ on the Mohs Scale
Just a few things in my personal collection
Amethyst (7)
Citrine (7)
Smoky Quartz (7)
Agate (7)
Jasper (7)
Carnelian (7)
Chrysoprase (7)
Onyx (7)
Moss Agate (7)
Bloodstone (Heliotrope) (7)
Blue Chalcedony (7)
Topaz (8)
Spinel (8)
Aquamarine (7.5–8)
Garnet (6.5–7.5)
Tourmaline (7–7.5)
Sapphire and Ruby (Corundum, 9)
Diamond (10)
A Note about Tenacity
It’s easy to assume that a hard stone is automatically durable, but that isn’t exactly true. It’s important to consider both hardness and tenacity.
Hardness is resistance to scratching and abrasion.
Tenacity describes how well a material resists breaking, chipping, bending, or crushing.
For example:
Diamond is the hardest mineral on earth (Mohs 10) but has brittle tenacity, meaning it can cleave or shatter if struck sharply.
Jade (nephrite and jadeite) is softer (about Mohs 6–7) but has very high tenacity, making it exceptionally resistant to breakage.
Chalcedony varieties (like agate and jasper) also have good tenacity due to their dense microcrystalline structure.
Turquoise (Mohs ~5–6) is often softer and less tenacious. It always requires a bit of extra care. Stabilization can help create both hardness and tenacity.
Even a stone with high hardness can be damaged by impact. It’s especially important to protect your rocks from knocks or drops. Thoughtful setting design and mindful storage and wear are key.
Round Diamonds - Photo by Edgar Soto on Unsplash
She’s a 10 but acts like she invented luxury.
Not into diamonds? Maybe you’re looking for something ethical, more affordable, or unique, there are many diamond alternatives that still offer high durability. For a ring you want to wear everyday for 5, 10, 50+ years, I suggest you pick something with a Mohs hardness of at least 8. For someone like me who refuses to take their ring off and is no stranger to gardening, weightlifting, pool swimming, and traveling, I would recommend that you skip the 8’s and up the hardness to 9+.
Clear and Colorless Alternatives
Lab-Created Diamond
Hardness: 10
Notes: Chemically identical to mined diamonds. Comes in all colors (white, champagne, gray, yellow, pink). Often more affordable.
Moissanite
Hardness: 9.25
Notes: Lab-created, with exceptional brilliance and rainbow fire. Very durable and popular for engagement rings.
White Sapphire
Hardness: 9
Notes: A natural corundum. Less fiery than diamond, but bright and clean-looking. Excellent scratch resistance.
Cubic Zirconia (CZ)
Hardness: 8–8.5
Notes: Synthetic and inexpensive. Offers diamond-like sparkle but can dull or scratch more easily over time with regular wear. Good for statement pieces or occasional wear.
Colored and Included Alternatives
Diamonds and Sapphires with LOTS of flavor
If you’d rather embrace unique colors or natural inclusions, there are lots of options that still provide you with a mohs hardness of 8.
Salt & Pepper Diamond
Hardness: 10
Notes: Natural diamonds filled with visible inclusions—gray, black, and cloudy patterns. Every stone is unique.
Colored Diamonds
Hardness: 10
Notes: Diamonds naturally occur in a rainbow of shades—champagne, cognac, gray, yellow, pink, and more.
Sapphires & Rubies (Corundum)
Hardness: 9
Notes: While best known in blue, sapphires come in nearly every color, including white, pink, yellow, green, peach, and black. Rubies are simply red sapphires.
Spinel (Gray, Blue, Pink, Lavender)
Hardness: 8
Notes: Brilliant and durable, spinel is available in many rich colors. An underappreciated gem historically mistaken for ruby.
Chrysoberyl & Alexandrite
Hardness: 8.5
Notes: Very durable with excellent clarity. Most commonly yellow-green, but also found colorless in rare cases. Alexandrite, a form of chrysoberyl, is famous for dramatic color change from greenish in daylight to reddish under incandescent light.
Whether you’re designing a custom piece or just shopping for your collection, understanding hardness and the Mohs scale makes a big difference in how your rocks hold up over time. From everyday quartz dust in the air to accidental knocks on your workbench, your gemstones go through more than you’d think.
BUT Remember, it’s not just about choosing the hardest gem. There are many factors to consider when creating a new piece. Soft and beautiful stones like opals and turquoise can still be great options if the jewelry will be worn only occasionally, cared for meticulously, or designed as earrings where they won’t take as much abuse.
Happy Rock Hunting! - Kelly