Gemstone Hardness Compared
A Complete Hardness Chart of Popular Gemstones
Each mineral has its own hardness value. The Mohs scale is used worldwide to understand the hardness of stones.
The Mohs scale is a ten-point scale of relative surface hardness of minerals. The hardness of a mineral is determined as follows: there are a set of 10 reference stones (etalons); if the mineral scratches the surface of a reference stone from the scale, its hardness is represented as higher; if its surface is scratched by the reference mineral, its hardness is lower.
Some stones have a single-digit hardness value, such as diamond (10/10) whereas some have values such as 7-7.5. The scale is used to evaluate minerals and to compare relative hardness.
Interestingly, the scale and method for determining the hardness of minerals was proposed in 1811 by the German mineralogist Friedrich Mohs and is still in use today. Of course, it is important to note that the Mohs scale only informs us about the relative hardness of minerals.
We have compiled a list of more than 10 of the most famous stones and here you will find their gemstone hardness compared across the Mohs Scale, in order from the strongest, to the weakest.
Interestingly, the scale and method for determining the hardness of minerals was proposed in 1811 by the German mineralogist Friedrich Mohs and is still in use today. Of course, it is important to note that the Mohs scale only informs us about the relative hardness of minerals.
1. DIAMOND - 10/10
This is the hardest of mineral gemstones! Named the true king of gems, it is called “eternal”, “indestructible”. This is all because of its extremely high hardness, which is ranked the highest at a value of 10.
Diamonds are transparent often colorless minerals, occasionally having yellow or pink hues, and carry a bright luster, with high indices of light refraction.
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2. RUBY- 9/10
A ruby, much like a diamond, has a high hardness at 9 points. In general, rubies are a variety of red corundum. Blue corundum is known as sapphires.
Rubies are one of the most expensive stones, with colors ranging from dark pink to dark red, and some are also found with a violet hue. It is worth mentioning that synthetic rubies are often used in high-end watch movements or in laser systems.
3. AQUAMARINE - 7.5-8/10
The hardness of an aquamarine stone is enviable, reaching eight out of ten points on the Mohs scale. The stone is transparent and has a glassy luster, with a blue or green hue.
The stone belongs to the beryl family, and because of its color and transparency, it is associated with the sea and water. This is reflected in its name, which literally translates from Latin for “sea water.”
It is worth mentioning that the hardness and clarity of the stone makes aquamarine one of the more favorite among cutters. They can experiment with different forms of cuts without any fear of spoiling the stone.
4. GARNET - 6.5/7.5/10
Garnets have a reasonable hardness level, although values vary between varieties. They are commonly associated with dark red colored stones, but in reality, garnets can also be green, orange, or even a variety that changes color. The stone may or may not be transparent, but any quality garnet has a beautiful luster.
In addition to jewelry, garnets are used a lot in industry, such as its addition to building mortar, or its use in laser systems.
5. OPAL - 5.5-6.5/10
Opal is a mineraloid of various shades that contains a high water content (sometimes up to 10%). Opal is of medium hardness and should therefore be treated with care, as its increased water content may cause cracks, or a loss of color. It is best to be stored in a place where there are no sudden temperature fluctuations, as well as a location where the air is not too dry.
6. MOONSTONE - 6.5/10
Moonstone is another mineral of many shades: blue, white, peach, pink, gray, etc. Its main feature that moonstone is loved for is its internal play of light - adularescence. Unfortunately, the stone does not have the highest hardness at just 6-6.5, but there is no need to worry. Experience shows that moonstones can be worn in jewelry for an exceptionally long time. The main thing is to take good care of the stone, and to clean and maintain it regularly.
7. LABRADORITE - 6.5/10
Labradorite is a blue-colored mineral with a unique, stunning effect - labradorescence, which is the shimmering of light inside the stone. The hardness of the mineral is the same as that of the Moonstone, which is 6-6.5, and, of course, this means it too requires care. It is worth mentioning that the two stones are remarkably similar in color, hardness, and effects inside the stone.
8. LAPIS LAZULI - 5.5/10
Lapis lazuli is a stone of heavenly color with incredibly beautiful golden inclusions, which resemble the starry sky. This mineral belongs to the group of silicates. As the stone is not extremely hard, it can be prone to scratches. Which is why it is important to take special care of it.
Lapis lazuli is often used not only for jewelry, but also for figurines and jewelry boxes. In the past, lapis lazuli was used to make the bright blue coloring pigment you can see in old paintings.
9. DOLOMITE - 4-4.5/10
The mineral dolomite has a hardness of only 4-4.5. This is quite a low hardness, so the stone is rarely used in jewelry, as the piece would be too fragile. As a decorative stone it is strong enough, but very brittle when exposed to physical contact with other materials, making it easily scratched or damaged. Its main use as a mineral is to make powder - dolomite flour. Which is used for industrial purposes, in metallurgy. Also, dolomite is used in various production areas, as an ingredient in preparations that help saturate the body's internal systems with calciu
10. BIOTITE - 2.5-3/10
Biotite is a very frequently occurring stone. Its large crystals are opaque, while its thin crystals are translucent and very fragile. The mineral has a low hardness, so it is rarely found in the jewelry.
Only large and well-formed crystals of biotite are used in the manufacturing of jewelry. The mineral is also used as an electrical insulator in various products. Biotite powder is also one of the components of cement and bronze paint.
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11. GRAPHITE - 1.5-2/10
This mineral is one of the native crystalline forms of carbon, along with diamond. Though at the same time, they are quite different in their physical properties and value. Diamond is the hardest mineral, while graphite, on the contrary, is at the lowest level, 1.5-2 on the Mohs scale.
Graphite is a black stone with a matte or metallic luster and is not used in jewelry, but it is widely found in many different spheres of human activity. In one shape or form, it is used not only in industry, but regularly in our everyday lives.
This is by no means a complete list of stones. Every other mineral also has its own hardness. So, it is important to understand, before you buy a piece of jewelry containing a stone, how hard it actually is. This will help you in deciding on how to take care of the piece and in some cases, if the hardness of a stone is too low, whether to even buy the item in the first place.
Kindly note that healing gemstone meanings are not prescriptions or healthcare information.
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