On the Mohs hardness scale — the standard measure of a mineral's resistance to scratching — moissanite scores 9.25. This places it above sapphire (9.0), above ruby (9.0), above topaz (8.0), above emerald (7.5–8.0), and above almost every other gemstone on Earth. Only diamond (10.0) is harder. Understanding why moissanite is so extraordinarily hard reveals something fascinating about the nature of silicon carbide — and why moissanite's hardness makes it uniquely suited for a lifetime of daily wear.
The Mohs Hardness Scale: What It Measures
The Mohs hardness scale, developed by German mineralogist Friedrich Mohs in 1812, measures a mineral's resistance to scratching by ranking minerals from 1 (softest, talc) to 10 (hardest, diamond). The scale is not linear — the difference in hardness between adjacent numbers is not equal. Diamond (10) is approximately 4 times harder than corundum (9, the mineral family that includes sapphire and ruby), and corundum is approximately 2 times harder than topaz (8).
The practical implication of the Mohs scale for jewelry is straightforward: a gemstone can only be scratched by a material that is harder than it is. A gemstone with a Mohs hardness of 9.25 can only be scratched by diamond (10.0) and by other moissanite stones. It cannot be scratched by sapphire, ruby, quartz, steel, or any of the materials encountered in daily life.
Why Silicon Carbide Is So Hard
Moissanite's extraordinary hardness comes from its crystal structure. Silicon carbide (SiC) — the mineral that moissanite is made from — forms a crystal lattice in which silicon and carbon atoms are bonded together in a tetrahedral arrangement, with each atom bonded to four others. This arrangement creates an extremely strong, rigid crystal structure that is highly resistant to deformation and scratching.
The silicon-carbon bond is one of the strongest chemical bonds in nature. Silicon carbide is used industrially as an abrasive (sandpaper, grinding wheels, cutting tools) and as a structural material in applications that require extreme hardness and heat resistance — including bulletproof vests, brake discs, and semiconductor devices. The same properties that make silicon carbide valuable in industrial applications make moissanite extraordinarily durable as a gemstone.
Moissanite vs. Other Gemstones: The Hardness Comparison
Diamond: 10.0 Mohs — the only material harder than moissanite
Moissanite: 9.25 Mohs — harder than every other gemstone except diamond
Sapphire & Ruby (Corundum): 9.0 Mohs — slightly softer than moissanite
Alexandrite & Chrysoberyl: 8.5 Mohs
Topaz: 8.0 Mohs
Emerald (Beryl): 7.5–8.0 Mohs
Quartz (including Amethyst, Citrine): 7.0 Mohs
Tanzanite: 6.5–7.0 Mohs
Opal: 5.5–6.5 Mohs
Pearl: 2.5–4.5 Mohs
The practical implication: household dust contains quartz particles (7.0 Mohs). Any gemstone softer than 7.0 Mohs will be gradually scratched by household dust during daily wear. Moissanite (9.25 Mohs) is completely immune to scratching by household dust, steel, or any material encountered in daily life.
What 9.25 Mohs Means for Daily Wear
Moissanite's 9.25 Mohs hardness means:
✅ It cannot be scratched by any material encountered in daily life except diamond
✅ It will not develop surface scratches from household dust, steel, or kitchen surfaces
✅ It will look as brilliant after 50 years of daily wear as it did on day one
✅ It is suitable for the most demanding daily wear environments — kitchens, clinics, gyms, outdoor activities
✅ It is covered by our Lifetime Gemstone Warranty — because we are confident it will never need to be replaced
Hardness vs. Toughness: An Important Distinction
Hardness (resistance to scratching) is different from toughness (resistance to breaking or chipping). Diamond is the hardest material on Earth but is actually less tough than moissanite — diamond can chip or cleave along its crystal planes if struck at the right angle. Moissanite's hexagonal crystal structure gives it excellent toughness as well as extraordinary hardness, making it one of the most durable gemstones available for daily wear.
Explore our collection — every stone DEF color, VVS1 clarity, GRA-certified, and backed by our Lifetime Gemstone Warranty.
🛡️ Lifetime Gemstone Warranty — Your stones are protected forever.
⬆️ Lifetime Upgrade Program — Upgrade your stones or metal anytime.
✏️ Request a Custom Design — Make it uniquely yours.
Related guides:
Can Moissanite Get Scratched?
Moissanite vs Diamond Under the Microscope
The Science of Silicon Carbide
Is Moissanite Good for Everyday Wear?
Does Moissanite Ever Lose Its Shine?