Mohs Hardness of Gemstones — Reference Scale
Hardness values for 130 gemstone species, sorted high to low. Includes hardness range and crystal system.
The Mohs hardness scale ranks the relative scratch resistance of minerals from 1 (talc) to 10 (diamond). In gemology it serves as a quick screening test and as a durability guide for setting and wear. Diamond at 10 is the hardest known natural material; corundum (ruby and sapphire) at 9 is hard enough to scratch quartz; feldspar at 6 is scratched by a steel file. The scale is ordinal, not linear — the difference in absolute hardness between 9 and 10 (diamond vs. corundum) is far greater than between any adjacent pair lower on the scale.
In field identification, hardness tests should be used with caution. Scratching a faceted gem can damage it; testing on an inconspicuous area with a reference mineral or steel probe gives only a rough bracket. A better field application is knowing which gems are too hard to be scratched by common objects: a steel file (6.5) will scratch anything below corundum; a quartz crystal (7) will scratch anything below 7. Gems below 7 (fluorite, apatite, calcite, amber, jet) require gentler handling and are more susceptible to abrasion in jewelry.
Some gem species show a range of hardness due to directional variation (cleavage direction vs. growth direction) or compositional variation within a species group. Kyanite, for example, is notably anisotropic: 4–5 parallel to the length and 6–7 across it. The table below shows the full published range for each species.
| Gem | Hardness Min | Hardness Max | Crystal System | Notes |
|---|---|---|---|---|
| Blue Diamond | 10 | 10 | Cubic | Blue color in Type IIb diamonds is caused by trace boron. Natural Type IIb diamonds are ex… |
| Brown Diamond | 10 | 10 | Cubic | Brown diamonds are the most abundant fancy color. Brown color arises from plastic deformat… |
| Diamond | 10 | 10 | Cubic | The hardest natural substance, known for its brilliance and fire. |
| Pink Diamond | 10 | 10 | Cubic | Pink color in diamonds arises from plastic deformation of the crystal lattice creating sli… |
| Yellow Diamond | 10 | 10 | Cubic | Yellow diamonds are Type Ia (Cape series, nitrogen in B-aggregates — most common natural f… |
| Moissanite | 9.25 | 9.25 | Hexagonal | All gem-quality moissanite in trade is synthetic silicon carbide (SiC), grown by CVD. Natu… |
| Color-Change Sapphire | 9 | 9 | Trigonal | Color-change sapphire is corundum colored by vanadium, shifting from blue or blue-gray in … |
| Padparadscha Sapphire | 9 | 9 | Trigonal | Pinkish-orange to orangey-pink corundum variety; color must show both pink and orange in b… |
| Pink Sapphire | 9 | 9 | Trigonal | Pink sapphire is chromium-colored corundum with insufficient saturation to qualify as ruby… |
| Ruby | 9 | 9 | Trigonal | Ruby is the red variety of corundum. Origin affects value and fluorescence: Burmese (Mogok… |
| Sapphire | 9 | 9 | Trigonal | Sapphire is any color of corundum except red (ruby). Origin affects value and fluorescence… |
| Star Ruby | 9 | 9 | Trigonal | Star ruby displays a 6-rayed star from three sets of rutile silk inclusions at 60° interva… |
| Star Sapphire | 9 | 9 | Trigonal | Star sapphire displays a 6-rayed star from three sets of rutile silk inclusions. Blue and … |
| Synthetic Color-Change Corundum | 9 | 9 | Trigonal | Vanadium-doped synthetic corundum sold as 'alexandrite' in estate jewelry since the mid-20… |
| White Sapphire | 9 | 9 | Trigonal | White sapphire is colorless corundum. As a diamond simulant, its main weakness is very low… |
| Yellow Sapphire | 9 | 9 | Trigonal | Yellow sapphire is iron-colored corundum (Fe³⁺). Sri Lankan and Burmese material often sho… |
| Alexandrite | 8.5 | 8.5 | Orthorhombic | The color-change variety of chrysoberyl, appearing green in daylight and red in incandesce… |
| Cat's Eye Chrysoberyl | 8.5 | 8.5 | Orthorhombic | Cat's eye chrysoberyl (cymophane) chatoyancy is caused by parallel growth tubes or rutile … |
| Chrysoberyl | 8.5 | 8.5 | Orthorhombic | A durable gemstone known for its brilliance. The cat's eye variety (cymophane) shows stron… |
| Cubic Zirconia | 8 | 8.5 | Cubic | Cubic zirconia (ZrO2) is entirely synthetic — no natural gem-quality cubic ZrO2 exists. Pr… |
| Taaffeite | 8 | 8.5 | Hexagonal | Taaffeite (BeMgAl₄O₈) was first identified as a new mineral species in 1945 after Count Ta… |
| YAG | 8 | 8.5 | Cubic | YAG (Yttrium Aluminum Garnet, Y₃Al₅O₁₂) is a man-made material with no natural counterpart… |
| Aquamarine | 7.5 | 8 | Hexagonal | Aquamarine is the light blue to greenish-blue variety of beryl. |
| Black Spinel | 8 | 8 | Cubic | A hard, durable, and singly refractive gemstone often used as a simulant for black diamond… |
| Emerald | 7.5 | 8 | Hexagonal | Emerald is the green to greenish-blue variety of beryl. |
| Goshenite | 7.5 | 8 | Hexagonal | Colorless beryl. Distinguished from quartz by higher RI and hardness; from white sapphire … |
| Heliodor | 7.5 | 8 | Hexagonal | The yellow to greenish-yellow variety of beryl, colored by iron (Fe³⁺). Also called Golden… |
| Morganite | 7.5 | 8 | Hexagonal | The pink to orange-pink variety of beryl, colored by manganese. |
| Phenakite | 7.5 | 8 | Trigonal | Beryllium silicate with unexpectedly high RI for its light weight. Occasionally sold as a … |
| Red Beryl | 7.5 | 8 | Hexagonal | Red beryl (bixbite) is colored by Mn²⁺ and found almost exclusively in the Wah Wah Mountai… |
| Spinel | 7.5 | 8 | Cubic | A durable, singly refractive gemstone that occurs in a wide range of colors. |
| Synthetic Spinel | 8 | 8 | Cubic | Flame-fusion synthetic spinel was the dominant birthstone simulant from the 1930s–1980s. E… |
| Topaz | 8 | 8 | Orthorhombic | A hard and durable gemstone available in a wide range of colors. |
| Almandine Garnet | 7 | 7.5 | Cubic | The most common garnet, known for its deep red to purplish-red colors. |
| Andalusite | 7 | 7.5 | Orthorhombic | Strong trichroism (green, red-brown, yellow-orange) is the primary diagnostic; color varia… |
| Chrome Tourmaline | 7 | 7.5 | Trigonal | Chrome tourmaline is colored by Cr³⁺ rather than iron, producing a rich emerald-like green… |
| Color-Change Garnet | 7 | 7.5 | Cubic | Pyrope-spessartite garnet with color change from blue-green or grey-blue in daylight to pu… |
| Danburite | 7 | 7.5 | Orthorhombic | Danburite is sometimes sold as a colorless diamond substitute or confused with colorless t… |
| Grandidierite | 7 | 7.5 | Orthorhombic | Grandidierite is an exceptionally rare borosilicate mineral from Madagascar displaying dia… |
| Green Tourmaline | 7 | 7.5 | Trigonal | Iron-bearing green tourmaline (verdelite) ranges from pale mint to deep forest green; Fe²⁺… |
| Grossular Garnet | 6.5 | 7.5 | Cubic | Grossular garnet ranges from colorless (leuco-grossular) to delicate mint green (Merelani … |
| Hessonite Garnet | 7 | 7.5 | Cubic | Grossular is a calcium-aluminium garnet; the orange-brown variety is called Hessonite. Und… |
| Indicolite | 7 | 7.5 | Trigonal | Blue to greenish-blue elbaite tourmaline. Separated from blue sapphire by much lower RI an… |
| Iolite | 7 | 7.5 | Orthorhombic | Famous for its extreme pleochroism, showing different colors when viewed from different di… |
| Low-Type Zircon | 6 | 7.5 | Tetragonal | A type of zircon whose crystal structure has been damaged by radioactive elements. |
| Malaya / Umbalite Garnet | 7 | 7.5 | Cubic | Malaya (or Umbalite) garnet is a pyrope-spessartite solid solution from the Umba River Val… |
| Paraiba Tourmaline | 7 | 7.5 | Trigonal | Paraiba tourmaline (elbaite) derives its neon blue-green to blue color from copper and man… |
| Pyrope Garnet | 7 | 7.5 | Cubic | Known for its fiery red color, pyrope is a member of the garnet group. |
| Rhodolite Garnet | 7 | 7.5 | Cubic | Pyrope-almandine solid solution (~2:1 ratio) with purplish-red to raspberry-red color. RI … |
| Rubellite | 7 | 7.5 | Trigonal | Saturated red to pink-red elbaite tourmaline. Key field separation from ruby: RI 1.624–1.6… |
| Spessartite Garnet | 7 | 7.5 | Cubic | Orange to reddish-brown garnet; the vivid orange variety from Namibia is commercially know… |
| Star Garnet | 7 | 7.5 | Cubic | Star garnet is the asteriated variety of almandine, displaying a 4-rayed star from two set… |
| Tourmaline | 7 | 7.5 | Trigonal | Elbaite tourmaline occurs in a wide range of colors with strong pleochroism. Named color v… |
| Tsavorite Garnet | 7 | 7.5 | Cubic | The green, chromium or vanadium-rich variety of grossular garnet. |
| Watermelon Tourmaline | 7 | 7.5 | Trigonal | Watermelon tourmaline (elbaite) has a pink to red core surrounded by a green rim. The grad… |
| Zircon | 7.5 | 7.5 | Tetragonal | A brilliant natural gemstone with high dispersion, not to be confused with cubic zirconia. |
| Agate | 6.5 | 7 | Trigonal | Banded chalcedony variety. Natural agate is typically grey-white with muted banding; vivid… |
| Amethyst | 7 | 7 | Trigonal | The purple variety of quartz, its color is caused by iron impurities and irradiation. Amet… |
| Ametrine | 7 | 7 | Trigonal | Bicolor quartz variety with zones of purple (amethyst) and yellow-orange (citrine) in a si… |
| Aventurine | 7 | 7 | Trigonal | A macrocrystalline quartz aggregate with flat platy inclusions (typically fuchsite mica fo… |
| Bloodstone | 6.5 | 7 | Trigonal | Dark green opaque chalcedony with distinctive red, orange, or yellow spots from iron oxide… |
| Carnelian | 6.5 | 7 | Trigonal | Orange-red to red-brown translucent chalcedony; color from iron oxide (hematite/goethite).… |
| Cassiterite | 6 | 7 | Tetragonal | A tin oxide mineral that is the most important ore of tin, rarely seen as a gemstone. |
| Chalcedony | 6.5 | 7 | Trigonal | Microcrystalline quartz aggregate. Generic chalcedony is translucent blue, grey, or white.… |
| Chrysocolla | 2.5 | 7 | Amorphous | A hydrated copper silicate, often found mixed with quartz which increases its durability. |
| Chrysoprase | 6.5 | 7 | Trigonal | Apple-green to yellow-green chalcedony; color caused by nickel silicate inclusions. Austra… |
| Citrine | 7 | 7 | Trigonal | The yellow to brownish-orange variety of quartz, often created by heat treating amethyst. |
| Demantoid Garnet | 6.5 | 7 | Cubic | The green variety of andradite garnet, prized for its exceptional brilliance and fire. "Ho… |
| Diaspore | 6.5 | 7 | Orthorhombic | Color-change diaspore marketed as Zultanite or Csarite shifts from kiwi green in daylight … |
| Hawk's Eye | 7 | 7 | Trigonal | Blue-grey to blue-green chatoyant quartz formed where crocidolite asbestos is replaced by … |
| Hiddenite | 6.5 | 7 | Monoclinic | Green chromium-bearing spodumene from North Carolina. True hiddenite (Cr-colored) is very … |
| Jadeite | 6.5 | 7 | Aggregate | The rarer and more valuable of the two minerals known as jade. |
| Kunzite | 6.5 | 7 | Monoclinic | The pink to lilac variety of spodumene, known for strong pleochroism and fluorescence. |
| Kyanite | 4.5 | 7 | Triclinic | Blue aluminum silicate commonly confused with sapphire or tanzanite. Uniquely among gemsto… |
| Onyx | 6.5 | 7 | Trigonal | True onyx is a parallel-banded chalcedony with alternating black and white layers. In trad… |
| Peridot | 6.5 | 7 | Orthorhombic | Known for its distinctive olive-green color and strong birefringence. |
| Pietersite | 6.5 | 7 | Aggregate | Trade name for a brecciated aggregate of hawk's eye (blue crocidolite-replaced quartz) and… |
| Prasiolite | 7 | 7 | Trigonal | Prasiolite is the pale green variety of quartz produced commercially by heat-treating or i… |
| Rock Crystal | 7 | 7 | Trigonal | The colorless and transparent variety of quartz. |
| Rose Quartz | 7 | 7 | Trigonal | The pink variety of quartz, usually found in a massive, translucent form. The color in mas… |
| Sinhalite | 6.5 | 7 | Orthorhombic | Sinhalite is a rare borate mineral first described as a gem species in 1952 (originally mi… |
| Smoky Quartz | 7 | 7 | Trigonal | The brown to black variety of quartz, colored by natural irradiation of aluminum impuritie… |
| Tanzanite | 6 | 7 | Orthorhombic | The blue to violet variety of zoisite, known for its striking trichroism. |
| Thulite | 6 | 7 | Orthorhombic | Thulite is a manganese-bearing pink variety of zoisite used primarily in ornamental work a… |
| Tiger's Eye | 7 | 7 | Trigonal | Chatoyant quartz formed by pseudomorphous replacement of crocidolite asbestos fibers with … |
| Amazonite | 6 | 6.5 | Triclinic | Blue-green microcline feldspar colored by lead and water; frequently sold as a turquoise a… |
| Benitoite | 6 | 6.5 | Hexagonal | Found almost exclusively in San Benito County, California, in association with neptunite a… |
| Black Opal | 5.5 | 6.5 | Amorphous | Black opal from Lightning Ridge, NSW, Australia is commercially the most valuable opal var… |
| Chrome Diopside | 5.5 | 6.5 | Monoclinic | Vivid grass-green chromium-bearing diopside sourced primarily from Russia/Siberia. Chelsea… |
| Fire Opal | 5.5 | 6.5 | Amorphous | Fire opal is the orange-to-red variety of opal from Mexico (principally Querétaro state), … |
| Hematite | 5.5 | 6.5 | Trigonal | An iron oxide with a high metallic luster and a characteristic red-brown streak. |
| Kornerupine | 6.5 | 6.5 | Orthorhombic | Rare borosilicate mineral from Madagascar, Sri Lanka, and Greenland. Green chromium-bearin… |
| Labradorite | 6 | 6.5 | Triclinic | Displays a spectacular iridescent effect known as labradorescence. |
| Moonstone | 6 | 6.5 | Monoclinic | Characterized by a billowy, bluish-white light effect called adularescence. IMPORTANT: "Ra… |
| Nephrite | 6 | 6.5 | Aggregate | A variety of actinolite-tremolite, known for its toughness and greasy luster. |
| Opal | 5.5 | 6.5 | Amorphous | Precious opal exhibits play-of-color from microscopic silica sphere diffraction. Common op… |
| Prehnite | 6 | 6.5 | Orthorhombic | Pale apple-green prehnite is common in estate jewelry as cabochons and beads, often confus… |
| Rainbow Moonstone | 6 | 6.5 | Triclinic | "Rainbow moonstone" is a widely used trade name for white or colorless labradorite (plagio… |
| Rhodonite | 5.5 | 6.5 | Triclinic | A manganese silicate known for its rosy pink color, often with black dendritic inclusions. |
| Scapolite | 6 | 6.5 | Tetragonal | Yellow and violet scapolite appear in estate jewelry and at gem shows, sometimes confused … |
| Sugilite | 5.5 | 6.5 | Hexagonal | A rare cyclosilicate mineral found almost exclusively at the Wessels Mine in the Kalahari … |
| Sunstone | 6 | 6.5 | Triclinic | A plagioclase feldspar (typically oligoclase or andesine) displaying aventurescence — a me… |
| Charoite | 5 | 6 | Monoclinic | A rare complex silicate mineral found only at the Murun Massif in Siberia. Named for the C… |
| Clinohumite | 6 | 6 | Monoclinic | Clinohumite is a rare magnesium iron silicate of the humite group, only occasionally facet… |
| Hackmanite | 5.5 | 6 | Cubic | Hackmanite is the tenebrescent variety of sodalite, a sodium aluminum silicate chloride mi… |
| Hauyne | 5.5 | 6 | Cubic | Hauyne (also spelled Haüyne) is a rare blue feldspathoid of the sodalite group, found prim… |
| Lapis Lazuli | 5 | 6 | Aggregate | A deep-blue metamorphic rock used as a semi-precious stone that is prized since antiquity. |
| Sodalite | 5.5 | 6 | Cubic | Opaque to translucent blue sodium aluminum silicate chloride; chemically distinct from lap… |
| Star Diopside | 5 | 6 | Monoclinic | Black asteriated diopside from India displaying a 4-rayed star from two sets of magnetite … |
| Turquoise | 5 | 6 | Triclinic | An opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminum. Bloc… |
| Enstatite | 5 | 5.5 | Orthorhombic | Chrome enstatite is a chromium-bearing orthorhombic pyroxene producing rich green color, f… |
| Moldavite | 5.5 | 5.5 | Amorphous | Tektite — natural glass formed ~14.8 million years ago by a meteorite impact in the Ries c… |
| Obsidian | 5 | 5.5 | Amorphous | A naturally occurring volcanic glass formed when lava cools rapidly. |
| Sphene | 5 | 5.5 | Monoclinic | Known for its exceptional dispersion which exceeds that of diamond, giving it incredible f… |
| Apatite | 5 | 5 | Hexagonal | Neon blue-green apatite from Madagascar is often confused with paraiba tourmaline or aquam… |
| Larimar | 4.5 | 5 | Triclinic | The blue gem variety of pectolite, found only in the Los Chupaderos mine area of Barahona … |
| Pearl | 2.5 | 4.5 | Aggregate | An organic gem formed within the soft tissue of a living shelled mollusk. |
| Variscite | 3.5 | 4.5 | Orthorhombic | A hydrated aluminum phosphate mineral prized as a green ornamental stone. Often confused w… |
| Coral | 3 | 4 | Aggregate | An organic gemstone formed from the skeletal remains of marine polyps. |
| Cuprite | 3.5 | 4 | Cubic | A copper oxide mineral known for its intense red color, but is too soft for most jewelry a… |
| Fluorite | 4 | 4 | Cubic | Known for its perfect cleavage in four directions and often strong fluorescence. |
| Jet | 2.5 | 4 | Amorphous | Organic gemstone formed from compacted driftwood (Araucaria trees) buried and transformed … |
| Malachite | 3.5 | 4 | Monoclinic | A green copper carbonate hydroxide mineral, known for its distinctive banded appearance. |
| Rhodochrosite | 3.5 | 4 | Trigonal | Manganese carbonate with intense rose-red to pink color and extreme birefringence. Best kn… |
| Serpentine | 3 | 4 | Monoclinic | Serpentine is the most common jade simulant in the trade, sold as 'new jade', 'Korean jade… |
| Sphalerite | 3.5 | 4 | Cubic | A zinc sulfide mineral with dispersion more than three times that of diamond, but is too s… |
| Howlite | 3.5 | 3.5 | Monoclinic | White to gray calcium borosilicate hydroxide with gray-black veining. Widely dyed blue or … |
| Ivory | 2.5 | 3 | Aggregate | Ivory is dentine from the tusks of elephants, mammoths, walrus, hippopotamus, and other ma… |
| Amber | 2 | 2.5 | Amorphous | Fossilized tree resin; low density and organic inclusions distinguish it from glass and co… |
| Cinnabar | 2 | 2.5 | Trigonal | A toxic mercury sulfide mineral with a bright scarlet to brick-red color, rarely used as a… |
See also: Full Reference Database · RI Chart · SG Chart · UV Fluorescence Chart
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