The ten hardest minerals ranked on the Mohs scale of mineral hardness, from diamond's perfect 10 down to the boundary with softer minerals at hardness 5.
Quick answer: 1. Diamond, 2. Corundum, 3. Topaz, 4. Quartz, 5. Orthoclase, 6. Apatite, 7. Fluorite, 8. Calcite, 9. Gypsum, 10. Talc.
The Mohs scale of mineral hardness, devised by German mineralogist Friedrich Mohs in 1812, ranks minerals by their ability to scratch another. It is an ordinal scale: each mineral can scratch those below it and be scratched by those above it. Apatite (hardness 5) marks the conventional boundary between "soft" and "hard" minerals. This list covers the ten hardest minerals on the standard Mohs scale, from diamond — the hardest natural material known — down through the ranks of corundum, topaz, and quartz. These minerals have practical significance far beyond geology: diamond and corundum are industrial abrasives, quartz drives timekeeping, and topaz is a gemstone standard.
The hardest natural material known, diamond is a crystalline allotrope of carbon. Its tetrahedral bonding network makes it exceptionally resistant to scratching. Beyond gemstone use, industrial diamonds are essential for cutting, grinding, and drilling.
A crystalline form of aluminium oxide that includes the gem varieties ruby (red) and sapphire (blue). It is roughly 9 times harder than its nearest neighbour, topaz, on the absolute hardness scale.
A silicate mineral of aluminium and fluorine, commonly found in pegmatites. Its hardness and range of colours make it a popular gemstone. Natural topaz is typically colourless, with blue and yellow hues often produced by heat treatment.
The most abundant hard mineral in the Earth's continental crust, composed of silicon dioxide. Its piezoelectric properties make it essential for timekeeping in quartz watches and electronic oscillators.
A potassium-rich feldspar mineral that is a major constituent of granite and other igneous rocks. It defines the hardness 6 reference and is the boundary between medium-hard and hard minerals.
A group of calcium phosphate minerals that is the primary source of phosphorus for fertiliser. In the Mohs scale it marks the conventional boundary at hardness 5: minerals this soft can be scratched by a steel knife.
A colourful calcium fluoride mineral that is the most popular mineral for collectors after quartz. It fluoresces under ultraviolet light — the property that gives it its name.
A calcium carbonate mineral and the primary constituent of limestone and marble. It defines the hardness 3 reference and exhibits strong double refraction, splitting light into two paths.
A soft calcium sulfate mineral that forms the basis of plaster and drywall. It can be scratched with a fingernail, making it notably softer than any mineral above it on the scale.
The softest mineral on the Mohs scale, talc is a hydrated magnesium silicate. It is the defining standard for hardness 1 and is ground into talcum powder. Its perfect cleavage and greasy feel make it easily identifiable.
| # | Name | Chemical Formula | Crystal System | Common Uses | Absolute Hardness |
|---|---|---|---|---|---|
| 1 | Diamond | C | Cubic | Gemstones, cutting tools, abrasives | 1,500 |
| 2 | Corundum | Al₂O₃ | Trigonal | Abrasives, gemstones, watch crystals | 400 |
| 3 | Topaz | Al₂SiO₄(F,OH)₂ | Orthorhombic | Gemstones | 200 |
| 4 | Quartz | SiO₂ | Trigonal | Electronics, glassmaking, gemstones | 100 |
| 5 | Orthoclase | KAlSi₃O₈ | Monoclinic | Ceramics, glass | 72 |
| 6 | Apatite | Ca₅(PO₄)₃(F,Cl,OH) | Hexagonal | Fertiliser, phosphoric acid | 48 |
| 7 | Fluorite | CaF₂ | Cubic | Flux in steelmaking, optics | 21 |
| 8 | Calcite | CaCO₃ | Trigonal | Construction, cement, neutraliser | 9 |
| 9 | Gypsum | CaSO₄·2H₂O | Monoclinic | Drywall, plaster, fertiliser | 3 |
| 10 | Talc | Mg₃Si₄O₁₀(OH)₂ | Monoclinic | Talcum powder, ceramics, paper | 1 |
Minerals are ranked by Mohs hardness value, where 10 is the hardest (diamond) and 1 is the softest (talc). The Mohs scale is ordinal — the intervals between values are not equal — but the ranking order is unambiguous. Only minerals included in Friedrich Mohs' original 1812 scale are listed, supplemented by the widely-accepted extension that includes corundum at 9 and diamond at 10. Each entry shows the standard reference mineral for its hardness level. Synthetic materials with higher hardness (e.g. aggregated diamond nanorods) are excluded as they are not natural minerals. Rank 1 is the hardest.
Diamond is the hardest natural mineral, rated 10 on the Mohs scale. However, several synthetic materials are harder: aggregated diamond nanorods (ADNRs) and wurtzite boron nitride can surpass diamond under certain conditions, but they are not naturally occurring minerals.
Diamond is the hardest natural material, meaning it resists scratching better than anything else found in nature. However, synthetic materials such as ultrahard fullerite and aggregated diamond nanorods have been engineered to exceed diamond's indentation hardness. Diamond is also brittle — a sharp blow can cleave it along crystal planes.
The Mohs scale from hardest (10) to softest (1) is: diamond (10), corundum (9), topaz (8), quartz (7), orthoclase (6), apatite (5), fluorite (4), calcite (3), gypsum (2), and talc (1).
The Mohs scale is ordinal — a mineral at hardness 6 is harder than one at 5, but the gaps between values are not equal. The absolute hardness scale uses a sclerometer to measure resistance to scratching in numerical terms. On that scale, corundum (Mohs 9) is about 4 times harder than quartz (Mohs 7), and diamond (Mohs 10) is about 15 times harder than corundum.