A Mohs Hardness Scale Gems Chart: Talc to Diamond

Every Mohs hardness scale gems chart you will come across goes back to one simple idea from 1812: a harder mineral scratches a softer one, and never the other way round. That single rule still shapes how jewelers choose stones for rings, how collectors store their pieces, and how geologists make a first guess at what a stone might be in the field. Below you will find the ten reference minerals, a chart of popular gems, why the numbers are not evenly spaced, and how to use all of it to wear and care for the stones you love.

What the Mohs Scale Measures (and What It Doesn’t)

The scale was introduced by the German mineralogist Friedrich Mohs in 1812. The idea of comparing stones by which one scratches the other is much older, though. The Greek writer Theophrastus mentioned it in his treatise On Stones around 300 BC, and Pliny the Elder returned to it in his natural history around AD 77. What Mohs did was turn that old habit into a fixed ladder of ten familiar minerals, so anyone could compare an unknown stone against the same reference points.

A few terms are worth settling before we go further:

• Hardness on this scale means scratch resistance only: how well a surface resists being marked by something else.
• Ordinal scale means the numbers show order, not size. A 9 is harder than an 8, but the scale does not tell you by how much.
• Toughness is a different property: how well a stone resists chipping, cracking or breaking when it is knocked or dropped.

That last point is where most confusion starts. A stone can sit high on the Mohs mineral hardness scale and still break if it is struck at the wrong angle. Diamond is the classic example: almost nothing scratches it, yet a hard knock can chip it. Meanwhile some softer materials hold together surprisingly well under impact. So whenever you see a hardness number beside a gem, read it as “how easily will this surface scratch?” and nothing more.

One more detail from the technical side: a “scratch” for Mohs purposes means a permanent mark you can see with the naked eye. Softer materials can sometimes leave microscopic damage on harder ones, but those tiny marks do not count when a hardness number is assigned. That is worth remembering if a published figure seems to clash with the faint wear you notice on an old, well-loved piece.

The Ten Reference Minerals

Each step of the Mohs scale of hardness of minerals is anchored by one reference mineral, most of them common in ordinary rocks. Every Mohs hardness scale gems list is built on these ten anchors. The table below lists them with their chemical formula and an “absolute hardness” figure measured with a sclerometer, an instrument that measures scratch resistance more precisely. Keep an eye on that last column, because it will matter in a moment.

Many collectors remember the order with a little rhyme or mnemonic of their own invention, but honestly the gem connections are an easier hook. If you know that quartz is 7 and corundum is 9, you can place most of your collection by asking “harder or softer than amethyst?” and “harder or softer than sapphire?”

Mohs Hardness Scale Gems Chart: Where Popular Stones Sit

Here is a practical Mohs hardness scale gems chart covering stones that turn up in jewelry boxes, crystal shelves and collector cabinets. Many gems are given as a range rather than a single number, because natural samples vary. A few everyday materials are included as reference points.

A few things jump out once you read the chart slowly. The whole quartz family, which you can explore in our Quartz & family section, clusters around 6.5 to 7. That covers clear quartz, amethyst and citrine at a clean 7, plus chalcedony and jasper just below. Moon and light favorites like labradorite sit a step lower at 6 to 6.5 (more in our Moon & light collection). Much-loved blue stones such as lapis lazuli and turquoise land at 5 to 6, softer than window glass at the low end. And selenite, sold everywhere as wands and towers, sits right down at 2 with the gypsum it belongs to.

Notice too that gold and silver are only 2.5 to 3. The metal around a gem is often far softer than the stone itself, which is why settings wear and prongs need checking long before a sapphire shows a mark. A hardness number alone never tells the whole story of a ring until you look at the metal as well.

Why the Gaps Between Numbers Are Uneven

Because the scale is ordinal, the steps between numbers are not equal. This is the detail many Mohs hardness scale gems charts skip. Go back to the absolute hardness column in the reference table. From talc (1) to gypsum (2) the measured value doubles from 1 to 2. From quartz (7) to topaz (8) it jumps from 100 to 200. Corundum (9) reaches 400, about twice topaz. Then diamond leaps to 1500, roughly four times as hard as corundum.

In plain terms, the single step from 9 to 10 is a far bigger leap than the whole climb from 1 to 7. That is why ruby and sapphire, impressive as they are, still sit in a completely different league from diamond.

The uneven spacing has practical consequences:

• Half points can hide big differences. A gem rated 8.5 is not “almost a 9” in absolute terms; the gap may be wider than it looks.
• Ranges matter. A stone listed as 5.5 to 6.5, like opal, can behave quite differently from piece to piece.
• Rocks do not have one true number. A rock is a mixture of minerals, each with its own hardness. Granite is sometimes given 6 to 7, but it is really a blend of quartz, feldspar, mica and other minerals. Any gem material that is a mixture can show soft and hard patches side by side, so polished surfaces may wear unevenly.

So a Mohs rock hardness scale figure for a mixed stone is best read as a rough average, not a promise.

Is a 7 on the Mohs Scale Good for Jewelry?

This is the question behind most interest in the Mohs hardness scale gems ranking, and the honest answer is: yes, a 7 is a solid, practical hardness, with a few caveats.

A gem at 7 is harder than ordinary steel (about 4 to 4.5), glass (about 5.5) and most metals, so the knocks and brushes of daily life will not easily mark it. That is a big part of why amethyst and citrine have been jewelry favorites for so long. What a 7 does not protect against is contact with harder material: another quartz gem, a topaz, or a diamond in the same box. Over years of daily ring wear, facet edges can soften and the polish can dull.

A rough guide many jewelers and collectors use when sorting gems into wear categories:

• 8 and above (diamond, sapphire, ruby, spinel, topaz): comfortable for rings worn every day.
• 7 to 8 (quartz family, tourmaline, garnet, emerald): good for rings with some care; ideal for pendants and earrings.
• 5.5 to 7 (opal, labradorite, peridot, tanzanite): better in protective settings or pieces that take fewer knocks.
• Below 5.5 (turquoise, fluorite, malachite, pearl, amber): pendants, earrings, brooches and occasional wear.

Remember toughness too. Emerald rates a respectable 7.5 to 8, yet many emeralds have inclusions that make them more prone to chipping than the number suggests. Hardness is the first question to ask about a gem, not the last.

The Hardest Gems on the Mohs Scale

If you want the top of any Mohs hardness scale gems ranking at a glance, here are the hardest gems most people will ever handle, in order:

1. Diamond (10). Pure carbon, and the mineral that defines the top of the scale.
2. Moissanite (about 9 to 9.5). Almost always lab-grown in jewelry, and harder than any natural gem except diamond.
3. Ruby (9). Red corundum.
4. Sapphire (9). Corundum in every other color, from blue to yellow to pink.
5. Alexandrite (8.5). The color-changing variety of chrysoberyl.
6. Chrysoberyl (8.5). Including its cat’s eye forms.
7. Taaffeite (8 to 8.5). A collector’s rarity more than a jewelry staple.
8. Spinel (8). Often mistaken for ruby in historic jewels.
9. Topaz (8). The reference mineral for 8.
10. Emerald and aquamarine (7.5 to 8). Both members of the beryl family.

Among the ten reference minerals themselves, the top three are diamond, corundum and topaz. If you are curious how hardness lines up with price, the short version is that it does not line up neatly at all; our piece on the five most expensive types of gemstone shows how much rarity and color matter instead.

In crystal traditions, hardness sometimes colors how people think about a stone’s character. Harder stones are often described as steady, enduring companions, the kind of piece people keep on them through a long day, while very soft stones like selenite are more often kept in one place on an altar or windowsill. That is symbolism layered over a physical fact, and it is a lovely way to remember which gems travel well and which prefer to stay home. You can read more about how we treat these traditions on our editorial page.

How Hardness Is Tested, and Why Not to Test Your Own Stones

The numbers on a Mohs hardness scale gems chart come from a simple method. Geologists use scratch kits containing a sample of each reference mineral, then find the hardest mineral the unknown sample can scratch, or the softest mineral that can scratch it. If apatite scratches your sample but fluorite does not, the sample’s hardness falls between 4 and 5. Field geologists still rely on this because it is quick, cheap and needs no electricity, even though it is not precise enough to predict how a material holds up in industry.

A worked example on the Mohs scale mineral hardness ladder

Say a geologist picks up a pale purple crystal on a hike. It scratches glass easily, which puts it above about 5.5. A quartz test piece does not scratch it, and it does not scratch quartz either: so it is close to 7. Combined with its six-sided crystal shape and glassy shine, quartz (amethyst) becomes the obvious first guess. Hardness narrowed the possibilities; other clues confirmed them.

Why you should skip this at home

A scratch test is destructive by design. It leaves a permanent mark, and on a faceted gem or a polished tumble that mark is exactly what you do not want. Pressing hard on a brittle crystal can also chip or split it, and some minerals are best not handled roughly at all (our guide to toxic crystals explains which ones). If you want to name a stone, start with non-destructive clues: color, luster, shape, weight in the hand and where it came from. Our crystal identification guide walks through those steps, and the background on crystals versus gemstones helps when labels get confusing.

If you would like a small set of stones to study side by side and learn by eye, the Crystal Kits at Spirit Magicka, the journal’s own shop, are an easy way to start a comparison tray. Keep any test you do try to rough, unpolished pieces you are happy to mark.

Using Hardness to Store, Clean and Display Your Collection

This is where the Mohs hardness scale minerals ranking pays off every day. Since harder stones scratch softer ones, how you store things matters more than almost anything else.

A worked example: one jewelry box, four pieces

Picture a box holding a diamond stud, an amethyst ring, an opal pendant and a turquoise bracelet, all tumbled together in one tray. Using the Mohs hardness scale gems chart above:

• The diamond (10) can scratch every other piece.
• The amethyst (7) can scratch the opal (5.5 to 6.5) and the turquoise (5 to 6).
• The opal can mark the turquoise at the softer end of its range.
• The turquoise is the most at risk and scratches none of the gems.

The fix is simple: give each piece its own pouch or compartment, and never let the diamond and the softer stones ride loose together. That one habit protects a collection more than any polishing cloth.

Everyday care by hardness band

A few common mistakes are worth avoiding:

• Mixing a crystal bowl. A bowl of loose tumbles looks lovely, but quartz pieces will slowly scuff softer ones. Group stones by hardness or line the bowl with cloth.
• Assuming hard means unbreakable. Points, terminations and the delicate tips on clusters can chip even on hard stones. Display clusters and geodes where they will not be bumped, and lift them by the base.
• Putting soft stones in water rituals. Some cleansing practices involve water or salt. Soft or water-sensitive stones can lose their polish or worse, so check a stone’s own page in our crystal library before trying any water method, and never make drinks with crystals placed directly in them.
• Carrying soft stones loose in a pocket. Keys and coins are harder than many soft gems. A small pouch makes pocket stones last much longer; this is also where tiny pieces like Mini Gemstones from Spirit Magicka are handy for daily carrying, kept in a soft pouch of their own.
• Forgetting the setting. Gold and silver are softer than nearly every gem they hold. Check prongs and bezels now and then, especially on rings.

Many people choose stones for meditation, a desk or a bedside table based on their meaning in crystal traditions. Hardness simply tells you where that stone will be happiest: a 7 in your pocket, a 2 on a quiet shelf. For deeper toughness notes and care routines for individual gems, see our companion piece on Mohs hardness, toughness and care, and browse the rest of the library under Earth treasures.

Once you know the ten reference points, the Mohs hardness scale gems ranking stops being a list to memorize and becomes a quiet habit: a glance at a stone, a rough sense of where it sits, and a good idea of how to keep it looking the way it did the day it caught your eye.