First: what are these numbers?

What Is the Mohs Hardness Scale?

The Mohs scale is a mineral hardness scale used to compare how resistant one mineral is to being scratched by another.

It runs from 1 to 10.

Talc sits at 1. Diamond sits at 10. Minerals higher on the scale can generally scratch minerals that sit lower on the scale.

From talc to diamond

The Mohs Scale Explained Simply

The bit you actually came for

Common Crystal Hardness Chart

Remember that natural specimens can contain inclusions, fractures, matrix material and mixed mineral content. Two pieces sold under the same crystal name may not behave identically.

Gorgeous. Delicate. Do not bully them.

Which Crystals Are Soft?

Crystals sitting lower on the Mohs scale need more thoughtful handling, particularly when they are stored beside harder stones.

More durable does not mean invincible

Which Crystals Are Harder?

Quartz varieties sit at around 7 on the Mohs scale, making them more resistant to scratching than many softer collector crystals.

• Clear quartz: around 7.
• Amethyst: around 7.
• Rose quartz: around 7.
• Citrine: around 7.
• Agate: generally around 6.5–7.
• Jasper: generally around 6.5–7.
• Tiger's eye: generally around 6.5–7.

This is where people get themselves into trouble

Does a High Mohs Score Mean a Crystal Is Safe in Water?

No.

Hardness tells you about scratch resistance. It does not give you a complete answer about chemical stability, porosity, coatings, inclusions, fracture risk or whether a mineral should be repeatedly soaked.

Be particularly cautious with:

• Selenite and other gypsum varieties.
• Calcite.
• Malachite.
• Pyrite.
• Minerals with metallic components.
• Porous or crumbly specimens.
• Dyed, coated, glued or treated pieces.
• Jewellery where water can affect the setting, elastic, wire or adhesive.

If your goal is simply to cleanse a crystal energetically, there is rarely a compelling reason to gamble the physical piece.

Read our complete guide to cleansing crystals for safer options.

Salt is not a universal crystal spa treatment

Can You Put Crystals in Salt?

Salt can be abrasive and may interact badly with some minerals, finishes, jewellery components and delicate surfaces.

Salt water introduces another layer of potential problems because now you have both moisture and salt involved.

Australian sun is not playing around

Can Crystals Be Left in Sunlight?

Hardness does not tell you whether a crystal's colour will tolerate prolonged sunlight.

Some coloured minerals may fade with extended UV exposure. Amethyst is one of the best-known examples.

And if you are in Dubbo, regional NSW or anywhere else dealing with strong Australian summer sun, “just leave it on the windowsill all day” is not automatically good crystal care.

• Do not assume harder crystals cannot fade.
• Avoid unnecessary prolonged direct sunlight for colour-sensitive pieces.
• Do not leave crystal spheres where they could concentrate sunlight and create a fire risk.
• Use indirect light when you are unsure.

For intentional charging methods, read our guide to charging crystals safely .

Because jewellery gets knocked around

Crystal Hardness and Jewellery

A crystal sitting beautifully on a shelf has a very different life from a stone worn on your hand every day.

Rings are exposed to benches, doors, bags, water, cleaning products and everything else your hands encounter. Bracelets bang against desks. Pendants usually receive less impact but can still scratch against other jewellery.

And please remember: the hardness of the stone tells you nothing about whether the chain, elastic, adhesive or metal setting wants to join you in the shower.

Stop throwing everything into one bowl

How to Store Crystals Without Scratching Them

If harder and softer crystals are stored together, the harder pieces may scratch softer surfaces.

• Store delicate pieces separately.
• Use soft pouches for polished stones and jewellery.
• Keep fragile points and clusters where they cannot knock together.
• Do not stack heavy specimens on delicate pieces.
• Keep moisture-sensitive minerals somewhere dry.
• Protect colour-sensitive pieces from prolonged direct sunlight.

Physical cleaning and energetic cleansing are different things

How to Clean Crystals Safely

If a crystal is physically dusty, start with the least aggressive cleaning method possible.

• Use a clean, soft, dry cloth for polished surfaces.
• Use a very soft brush for suitable textured specimens.
• Avoid soaking when the mineral is unknown.
• Avoid acids, bleach and aggressive household chemicals.
• Do not scrub soft minerals with abrasive materials.
• Check specific mineral care before using water.

For energetic cleansing, you can often use methods that do not involve physically stressing the crystal at all.