What opal is, mechanically
Three facts explain almost everything about how opal behaves in wear.
- It is soft-ish. Opal sits around 5.5 to 6.5 on the Mohs scale. Quartz — which is in dust, sand and most countertops — is a 7; diamond is a 10. A steel knife blade will scratch opal.
- It is brittle rather than tough. Opal has no cleavage planes, so it does not split, but it does chip. A sharp knock at the edge of the stone is the real risk, not gradual abrasion.
- It contains water — as part of its structure. Opal carries roughly 3 to 21 per cent water by weight, typically around 6 to 10 per cent. That water is not contamination; it is why the stone is what it is.
The practical consequence is counter-intuitive: the enemy is rarely the knock you worry about. It is heat, dryness and chemicals.
Crazing: the failure mode worth knowing
Crazing is a network of fine internal cracks that can develop when a stone dries out too fast or meets a sudden temperature change. It looks like a faint haze or a spiderweb inside the stone, and it dulls the play-of-colour permanently — it cannot be reversed.
The usual causes are unglamorous: a hot car, a hairdryer, washing-up water, or years in a very dry place. If a stone is going to craze, it usually does so early and then stays stable. This is one good reason to avoid storing opal long-term in a bank vault or a dehumidified safe — dry conditions are not neutral where opal is concerned.
If your opal is Ethiopian, read this part
Much Ethiopian opal is hydrophane: it absorbs water readily. While it is wet, the stone can go milky or translucent and appear to lose its colour. As it dries, the colour comes back.
That is not damage in itself — but the wet-and-dry cycle is where the risk lives. Rapid drying, especially with heat, is what cracks hydrophane opal. So: do not soak it, do not dry it with a hairdryer, and if it does get wet, let it return to normal slowly, at room temperature, out of the sun.
It is also a real reason some buyers choose Australian opal for a ring and keep Ethiopian material for pendants, where it never meets water.
Why the setting matters more than the stone
This is the part most durability advice gets wrong. On a stone of 5.5–6.5 hardness, the setting does more for the stone's survival than any property of the opal itself.
- A bezel beats prongs. A bezel is a continuous rim of metal around the stone. It covers the girdle — the exposed edge where chips start — and spreads any impact across the whole rim. Prongs leave that edge in the open.
- A lower dome survives better than a tall one. Less height means less leverage on the edge when something hits it.
- Boulder opal is the tough option. Because the ironstone host stays attached as a backing, the stone has structure behind it that a free-cut opal simply does not. For a ring worn every day it is the most sensible precious opal there is — see opal types explained.
Where opal is genuinely fine, and where it isn't
Fine, without thinking about it: pendants, earrings, brooches, and rings you wear occasionally. Kept in a protected setting, these last for decades.
Needs a little discipline: a ring you wear every day. Typing at a desk is harmless. Moving furniture, gardening, lifting weights, or playing a sport with your hands is not. It is not the day that wears a stone down; it is the two minutes you forgot.
Take it off: swimming and hot tubs (chlorine), showers and washing up (soap and heat), cleaning with chemicals, gardening bare-handed, and the gym.
The care rules, in one list
- Never use an ultrasonic cleaner, steam, or an ammonia-based jewellery dip. All three are hostile to opal.
- Wipe with a soft dry or barely damp cloth. For solid Australian opal a brief wipe with lukewarm water and a trace of mild soap is generally fine — dry it immediately. For Ethiopian (hydrophane) opal, skip the water and use the dry cloth only.
- Jewellery goes on last and comes off first. Perfume, hairspray and cosmetics are all bad for it.
- Keep it away from prolonged heat and direct sun. A car dashboard in summer is the classic way to ruin an opal.
- Store it separately, in a soft pouch. In a jewellery box, opal is almost always the softest thing in there.
- Don't store it long-term somewhere very dry. Opal does not like desiccation.
If it does craze, chip, or dull
Crazing cannot be undone. The stone stays structurally stable but the colour is quieter, and the value drops with it.
A chip can sometimes be repolished out, which means removing material from the stone — worth doing on a valuable opal, rarely worth it on a modest one. Badly crazed stones are sometimes stabilised with resin, but that changes the stone permanently and should always be disclosed if it is ever sold on.
The honest summary
Opal is a 5.5-to-6.5 stone with water inside it. Treat it accordingly and it will outlast the fashion for it.
If you want one sentence to remember: the setting protects the stone, and heat and dryness are what actually hurt it.