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Crystal Hardness Chart: Mohs Values for 40 Popular Crystals

By Digital Towns Crystals ยท Last reviewed October 8, 2026

Short answer: most shop crystals fall between Mohs 2 and 8. Selenite (gypsum) sits at 2, calcite at 3, fluorite at 4, lapis around 5.5, moonstone and amazonite at 6, every quartz variety (amethyst, citrine, rose quartz) at 7, tourmaline at 7 to 7.5 and topaz at 8. Anything at 6 or below can be scratched by quartz grit, so store soft pieces apart. The full chart below gives each crystal's mineral name, Mohs value and specific gravity, with a source for every number.

How should you read a Mohs number?

A Mohs value is a rank, not a measurement. Minerals.net describes the scale as ten minerals, each harder than the one before, from talc to diamond, and notes that hardness is almost always rounded off to the nearest half number. A value such as "3.5 to 4" therefore means the mineral scratches a 3 but is marked by a 4 or a little above it. The gaps between ranks are wildly uneven: Geology.com points out that corundum and diamond are only one unit apart on Mohs yet enormously different when hardness is measured by indentation instead.

Three practical rules follow from that:

  • Equal or higher wins. A crystal can scratch anything with a lower number. Keep a quartz point and a fluorite octahedron in the same bag and the fluorite loses.
  • Ranges are honest. Many minerals vary with chemistry and direction, so a single number is often a simplification. Kyanite is the classic case, discussed below.
  • Hardness is not toughness. Geology.com separates the two: hard materials often break under stress, which is a lack of toughness, while others crumble, which is a lack of strength. A 7.5 tourmaline still snaps across its length if dropped.

If you want to test a stone yourself rather than read a chart, the step by step method, tools and safe spots are covered in Mohs hardness testing. This page is the reference table.

The ten index minerals

The scale is anchored by ten reference minerals. Specific gravity (SG) is added from Webmineral, which lists talc at hardness 1 with a density of 2.7 to 2.8.

Mohs Index mineral Crystal shop example SG (average)
1 Talc Soapstone carvings 2.75
2 Gypsum Selenite, desert rose 2.3
3 Calcite Honey, blue and optical calcite 2.71
4 Fluorite Rainbow fluorite 3.13
5 Apatite Blue apatite 3.19
6 Orthoclase Moonstone (orthoclase variety) 2.56
7 Quartz Amethyst, citrine, rose quartz 2.62
8 Topaz Topaz crystals 3.55
9 Corundum Ruby, sapphire 4.05
10 Diamond Diamond 3.51

The full crystal hardness chart

Sorted from softest to hardest. Where two references disagree, both values are shown. SG figures are averages or single values from Webmineral; "n/a" means the source page gives no figure for that material.

Crystal (trade name) Mineral Mohs hardness SG Source
Selenite, satin spar Gypsum 2 (Geology.com: 1.5 to 2) 2.3 Webmineral gypsum
Mica, muscovite Muscovite 2 to 2.5 2.82 Webmineral muscovite
Pink or blue halite Halite 2.5 (Geology.com: 2 to 2.5) 2.17 Webmineral halite
Lepidolite Lepidolite 2.5 to 3 2.84 Webmineral lepidolite
Chrysocolla Chrysocolla 2.5 to 3.5 2.15 Webmineral chrysocolla
Calcite (all colors) Calcite 3 2.71 Webmineral calcite
Wulfenite Wulfenite 3 6.75 Webmineral wulfenite
Celestite, angelite geodes Celestine 3 to 3.5 3.95 Webmineral celestine
Barite Barite 3 to 3.5 4.48 Webmineral barite
Rhodochrosite Rhodochrosite 3 (Geology.com: 3.5 to 4) 3.69 Webmineral rhodochrosite
Malachite Malachite 3.5 to 4 3.8 Webmineral malachite
Azurite Azurite 3.5 to 4 3.83 Webmineral azurite
Aragonite Aragonite 3.5 to 4 2.93 Webmineral aragonite
Stilbite Stilbite 3.5 to 4 2.15 Webmineral stilbite
Vanadinite Vanadinite 3.5 to 4 6.94 Webmineral vanadinite
Fluorite Fluorite 4 3.13 Webmineral fluorite
Apophyllite Apophyllite 4 to 5 2.34 Webmineral apophyllite
Kyanite Kyanite 4 to 7 (directional) 3.61 Webmineral kyanite
Turquoise Turquoise 5 to 6 2.7 Webmineral turquoise
Lapis lazuli Lazurite 5.5 2.4 Webmineral lazurite
Obsidian Volcanic glass about 5.5 n/a Geology.com obsidian
Opal Opal 5.5 to 6 2.09 Webmineral opal
Rhodonite Rhodonite 6 (Geology.com: 5.5 to 6.5) 3.6 Webmineral rhodonite
Sodalite Sodalite 6 (Geology.com: 5.5 to 6) 2.29 Webmineral sodalite
Moonstone Orthoclase 6 2.56 Webmineral orthoclase
Amazonite Microcline 6 2.56 Webmineral microcline
Labradorite Plagioclase 6 to 6.5 n/a Geology.com
Nephrite jade Nephrite 6 to 6.5 n/a Geology.com
Prehnite Prehnite 6 to 6.5 2.87 Webmineral prehnite
Hematite Hematite 6.5 (Geology.com: 5 to 6.5) 5.3 Webmineral hematite
Pyrite Pyrite 6.5 (Geology.com: 6 to 6.5) 5.01 Webmineral pyrite
Jadeite jade Jadeite 6.5 (Geology.com: 6.5 to 7) 3.3 Webmineral jadeite
Peridot Forsterite (olivine) 6 to 7 3.27 Webmineral forsterite
Kunzite Spodumene 6.5 to 7 3.15 Webmineral spodumene
Amethyst, citrine, rose and smoky quartz Quartz 7 2.62 Webmineral quartz
Garnet (almandine) Almandine 7 to 8 (Geology.com, garnet: 6.5 to 7.5) 4.19 Webmineral almandine
Black tourmaline Schorl 7.5 3.15 Webmineral schorl
Pink, green, watermelon tourmaline Elbaite 7.5 3.05 Webmineral elbaite
Aquamarine, emerald, morganite Beryl 7.5 to 8 2.76 Webmineral beryl
Topaz Topaz 8 3.55 Webmineral topaz
Ruby, sapphire Corundum 9 4.05 Webmineral corundum
Diamond Diamond 10 3.51 Webmineral diamond

Kunzite's hardness comes from Geology.com's list, which gives spodumene 6.5 to 7; the SG of 3.15 is Webmineral's figure. Labradorite and nephrite values come from the same Geology.com list.

Why do two references give different numbers?

Disagreement of half a step is normal and tells you something real. Hematite is listed at 6.5 on Webmineral but 5 to 6.5 on Geology.com. Rhodochrosite shows 3 on one and 3.5 to 4 on the other. Natural specimens vary, so when you plan storage or wear, assume the lower figure. Gypsum appears as 2 or 1.5 to 2, and the lower end matters: a fingernail marks selenite, which is why polished selenite towers pick up scuffs so fast and why storing it needs its own approach in storing selenite.

Kyanite is the extreme. Webmineral gives 4 to 7, and Minerals.net explains that scratched in one direction it shows a hardness of 4 to 5, while across that direction it shows 6 to 7. The same site calls kyanite the only mineral with such strong directional difference; in nearly every other mineral the effect is too weak to detect. If a kyanite blade seems "too soft", that is the reason.

Trade names cause the other kind of mismatch. Lapis lazuli is a rock, not a single mineral, so the 5.5 for lazurite describes its blue component only. Obsidian is a glass, and Geology.com puts it at about 5.5, adding that it lacks toughness and is easily broken or chipped on impact.

What does each hardness band mean for owning the stone?

Under 3: fingernail soft

Gypsum, halite, mica and lepidolite. These scuff from handling, fine dust and contact with almost any other crystal. Halite is also water soluble, so hardness is not its only weakness; water risk is a separate property, sorted mineral by mineral in water safe crystals. Dust with a dry soft brush and keep each piece in its own tray.

3 to 4.5: soft, often with cleavage

Calcite, celestite, barite, malachite, azurite, rhodochrosite, fluorite and the zeolites. Many have perfect cleavage, so a knock splits them along flat planes even when the surface resists light scratching. Barite and celestite are also heavy for their size (SG 4.48 and 3.95), which helps confirm them on a scale; the method is in the specific gravity test. Vanadinite and wulfenite, at hardness 3 to 4, are the densest crystals in the table at 6.94 and 6.75, so a small cluster feels surprisingly weighty in the hand.

5 to 6.5: medium, scratched by quartz

Lapis, turquoise, opal, obsidian, sodalite, moonstone, amazonite, labradorite and hematite. They take a good polish for display, but a quartz point, a quartz tumble or gritty dust will mark that polish, because quartz at 7 sits above all of them.

7 and above: hard, still not indestructible

Quartz varieties, garnet, tourmaline, beryl, topaz and corundum. They can still chip at a sharp termination or along a fracture, and they will scratch every softer stone stored beside them.

Shopping crystals across the hardness scale

Use the chart before you buy: a stone you plan to carry, use as a palm piece or keep in a pocket should sit at 6.5 or higher, while softer minerals are better as display specimens or spheres on a stand. Check that the listing names the actual mineral, since a trade name alone tells you little about hardness. These in-stock pieces cover most of the scale:

Digital Towns Market

Crystals across the hardness scale

See all crystals and minerals

Frequently asked questions

What is the softest crystal sold in crystal shops?

Talc, at Mohs 1, is the softest mineral on the scale and appears as soapstone carvings. Among popular crystals, selenite (gypsum, Mohs 2), mica and halite are the softest. A fingernail can mark all of them, so they need separate storage and gentle dusting.

Are amethyst, citrine and rose quartz the same hardness?

Yes. All three are varieties of quartz, which Webmineral lists at hardness 7 with a specific gravity of about 2.62 to 2.65. A pink, purple or yellow color does not change the hardness of the quartz underneath.

Which crystals are hard enough to wear every day?

Stones at 7 and above hold up best: quartz varieties, garnet, tourmaline, beryl (aquamarine, emerald), topaz and corundum (ruby, sapphire). Hardness only covers scratching, though. Toughness and cleavage also decide whether a stone chips, so settings that protect edges still matter.

Why does my selenite get scratched so easily?

Selenite is gypsum, rated 2 by Webmineral and 1.5 to 2 by Geology.com. Almost every other crystal, plus ordinary household dust, is harder. Store it on its own, dust it with a dry brush, and never tumble it with other stones.

Does a higher Mohs number mean a crystal is more valuable?

No. Hardness affects durability, not price. Vanadinite and wulfenite are soft at 3 to 4, yet fine clusters command high prices, while hard quartz is abundant and inexpensive. Rarity, color, crystal quality and locality drive value.

Sources