Onyx Worktop Maintenance: How to Keep This Special Material at Its Best

Onyx demands respect

Onyx is not the stone for someone who wants to forget about their worktop. It is a material defined by the combination of exceptional beauty and vulnerability — and those two are inseparable.

The translucency that makes onyx so unique is the same feature that makes it sensitive to damage. The wrong cleaner, a dropped perfume bottle or a mug of boiling water left too long: on another worktop these may be minor. On onyx they can leave visible traces.

That does not mean you cannot enjoy it. It means you know what you are bringing into your home.

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Why onyx is so different from other stones

Onyx is a calcite mineral, just like marble. On the Mohs scale it scores between 3 and 4 — soft for a worktop. For comparison: a knife or coin can easily scratch the surface. Granite sits at 6 to 7. The difference is enormous.

Onyx is also distinct because:

• It is more porous than most people expect
• It reacts to acids (lemon juice, wine, vinegar, coffee) — etching appears as dull marks
• Its layered structure means it can crack or fracture if struck or incorrectly installed
• Moisture can cause colour change if the stone is not properly impregnated

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Impregnation: not optional

A new onyx worktop must be impregnated before use. This also applies if the stone supplier says it has already been “treated” — ask exactly what that means and when it was done.

A good impregnator for onyx:

• Is specifically suitable for calcite-rich stones (not every impregnator is)
• Does not, or hardly, change the translucency or colour
• Is renewed annually for worktops under normal use

Test whether your worktop needs retreatment: place a small drop of water on the surface. If the water soaks in within 30 seconds without beading, the impregnation has worn out and you need to act.

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Daily maintenance

The golden rule: dry and pH-neutral.

• Use a soft microfibre cloth — no abrasive sponges, no coarse textiles
• Clean with lukewarm water and a pH-neutral stone cleaner — never vinegar, lemon juice or all-purpose cleaner
• Dry the worktop after every use — standing water is the main long-term enemy
• Use a trivet under hot pans or mugs — heat shock can cause hairline cracks in the surface layer

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What you must absolutely avoid

Do not do this	Why
Cut citrus fruit directly on the worktop	Citric acid immediately etches the surface
Use vinegar or wine vinegar as a cleaner	Chemical reaction with calcite, irreversible matt marks
Skip chopping boards	Even a blunt knife scratches onyx
Drop heavy objects	Onyx is brittle; cracks are often permanent
Leave the worktop wet	Discolouration and moisture penetration

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What to do if damage occurs

Etching (dull marks from acid contact): This is superficial damage to the calcite structure. A professional can polish or hone it in most cases — the result is excellent in 80 to 90 percent of cases, especially if the damage has not gone too deep. Do not wait too long: the longer etching remains, the deeper it can go.

Scratches: Depending on depth, superficial scratches can be polished out. Deep scratches that go through the entire polished layer require more work but are rarely completely beyond repair.

Cracks or breakage: This is the most difficult scenario to repair. A good stone restorer can inject and fill cracks, but a crack in onyx will always remain visible if you look closely. Prevention is the only real solution here.

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Backlighting and moisture damage

Backlit onyx is breathtaking — but it also reveals more. Moisture that has penetrated the stone is immediately visible with backlighting as darker or lighter zones. This is not a defect, but the result of insufficient or worn impregnation.

If you want backlighting, extra-careful impregnation is not a luxury but a requirement.

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Summary

Onyx is an investment — financially, but also in attention and care. With the right treatment and daily discipline, an onyx worktop can last for decades and remain a focal point. If you are careless with it, you will see that within a year as etching, stains and a dull surface.

Read more about natural stone finishes

All about etching on marble — similar behaviour to onyx

For those willing to give it that care, few things are more beautiful than well-maintained onyx.

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