Is opal fragile? Hardness, cracks and water

Opal knowledge · Durability

Hardness, setting, origin: what everyday wear actually needs

Is opal fragile? No, it does not shatter at the first knock. Setting and origin decide. A framed Australian opal from us is built for everyday wear. A freely hanging, unprotected stone, especially Welo, needs distance from chlorine and hairspray.

How hard is an opal, really?

An opal's hardness sits at 5.5 to 6.5 on the Mohs scale, and that scale measures only one thing: which material can scratch which other. Diamond sits at the end at 10, your fingernail at 2.5. Opal sits in the middle, and that is exactly where daily life gets interesting, because around 5.5 you find the things you deal with every day: knife blades, window glass, keys, coins.

The scale is not a set of scales. From 5 to 6 is a small step; from 9 to 10 is a huge one. You only need to remember one rule: anything harder than your opal can scratch it. Anything softer slides off.

The sentence to take from this table: the everyday enemy of opal is not a fall to the floor, but the dust on the table. Anyone who wipes a dusty stone bright with a sleeve is polishing it with quartz. That is how the fine scratches appear that leave an opal looking dull after years. How you spot that, and what the workshop does with it, is further down.

Crazing or a break: what is happening inside the stone?

Drying cracks, in the trade called crazing, are fine hairline cracks that form when an opal loses water faster than its structure can yield. A break is something else: an edge that gives way under a blow. To a layperson both look like “broken”, but they have different causes, different warning signs and different solutions.

Picture a rough opal that has come from twenty metres down. For millions of years it lay in damp rock at a steady temperature. Within a day it sits in forty-degree desert air. The outer layers give off water and shrink; the core stays damp; the tension looks for a path: the crack runs from the outside in. That is exactly why miners keep their rough stones in water, and exactly why serious cutters leave a rough opal to rest for months before they cut it. A stone that cracks in that time never becomes jewellery.

What most often arrives at the workshop is neither of those, but a scratched surface that wants repolishing. An opal that truly breaks almost always had two things at once: an unprotected edge and a hard landing.

May an opal go in water, and why do some have to stay wet?

Water is not an enemy of opal; it is a constituent: between 3 and 21 percent of its weight is water, in jewellery opals usually 6 to 10 percent. The stone is made of tiny silica spheres, and between them this water sits as in a very dense sponge. In Australian opals the sponge is closed: they take up no water and, under normal conditions, give none off. Washing hands, rain, a summer storm — none of it matters.

It is different with Welo opal from Ethiopia. It is hydrophane, literally “water-loving”; its pores stand open. If you dunk it, it soaks full within minutes. The play of colour fades; the stone turns milky or, depending on the stone, glass-clear. Anyone seeing that for the first time is sure the opal has lost its colour. It has not. As soon as the water evaporates, usually after one to two days, longer with large stones, the fire is back. Why that is so is set out in the article on Welo opal.

Can an opal dry out?

Yes, but not in your living room. A cut Australian opal holds its water content in normal room air for decades. What dries it out is not time, but heat plus dry air for hours: the glove box in high summer, the windowsill above a radiator, a safe with desiccant. There it loses water faster than the structure can follow, and that becomes the crazing above. Oiling it or storing it in water does not help. That is a ritual from the rough-stone world that, on polished jewellery, only leaves residue.

What does heat do to an opal?

Heat does not harm opal through temperature itself, but through the speed of the change and the water loss it triggers. An opal ring in summer sun on the finger is uncritical; your hand keeps it at body temperature. The same ring on the dashboard, where it can reach seventy degrees, is a risk. And the same ring in the sauna, followed by a jump into the plunge pool, is the classic among avoidable damages.

Does an opal fade in the sun?

No. The play of colour is not a pigment that could bleach; it is light diffracted at the silica spheres in the stone. There is no pigment the sun could break down. What counts in full sun is only the heat over hours — the parked car, not the walk.

Which setting protects an opal best?

A bezel setting is a closed metal rim that encircles the stone and stands a little proud of its edge; it protects an opal better than any other setting, because a blow hits the metal first. A prong setting holds the stone with four or six claws. It lets more light in, and the play of colour looks more open, but the edges stand free and take every door frame personally.

Besides the setting, three further things decide how much your piece can take:

For a ring worn every day, the bezel is therefore the sensible choice. What that means for the opal as an engagement ring is there, and which setting suits which finger is in Ring size and setting. Bezels and half-bezels for daily wear are in the collection Opal rings.

How much can your opal really take in daily life?

The everyday test is an honest stocktake in five questions you answer on your own stone, with no tools and no risk. Each question checks one of the points above: hardness, surface, water, setting and your habits. Tap a card to highlight it.

That is how honest the balance is: an opal is a stone for people who take it off for sport, cleaning and the garden, and in return wear something that does not exist twice. Anyone who does not want that is better served by a sapphire, and we say the same at Opal as an engagement ring.

What to do if something does happen?

A damaged opal is rarely a lost opal: scratches can be polished, a fracture edge can be recut, and even a replaced stone keeps its setting. Only crazing cannot be healed — but it can be stopped. Three steps, in this order:

1. Do not keep wearing it, do not glue it

   A cracked stone keeps working under every blow. And superglue makes any later repair impossible, because it soaks into the pores.

2. Sort it in raking light and photograph it

   Scratch, crack or break? A photo in daylight from above at an angle helps any workshop with a first assessment before the stone goes on its journey.

3. Take it to the workshop

   Scratches are repolished, a fracture edge is recut; the stone becomes a little smaller and the setting is adjusted. What is possible and what is not is in the workshop article Cutting, polishing and repairing opal. For a Liberty Angels piece, look first at the page on the 5-year guarantee to see which cases it covers, before you commission an outside workshop.

What gives you certainty beyond daily wear?

Certainty with opal has two sides: knowing what the stone can take, and knowing what you actually hold in your hand. Whether your stone can take a soak hangs on a question no everyday test can answer for sure: solid opal, doublet or triplet? That is exactly what a good certificate records.

Frequently asked questions about opal durability

If you are unsure or have questions, you are welcome to contact us at any time, even if you did not buy the opal from us. Contact form, email cs@libertyangels.de or call +49 171 1603048.