"Precious opal" is one of the few gem terms with a precise meaning, and it is worth knowing because it separates opal that is worth real money from opal that is not. Precious opal shows play of colour — the shifting spectral flashes that move as the stone turns. Common opal does not, however pretty its body colour may be. This stone is firmly in the first category.

The stone

3.50 carats, which is 3.85 ratti. Rs. 28,880, about Rs. 8,750 per carat, reference GS-000708. Recorded shape: oval. Origin: Ethiopia. One piece, as photographed.

What makes an opal precious

Structure, not chemistry. Precious and common opal are the same material — hydrated silica — but in precious opal the microscopic silica spheres are packed in a regular grid at close to the wavelength of visible light. That grid diffracts light into spectral colours, and because the effect depends on the viewing angle, the colours move as the stone does. In common opal the spheres are irregular or the wrong size, so no grid forms and no colour appears.

Measured from the photograph, colour flashes cover about 10% of this stone's face, sitting on a body that reads at a brightness of 202 out of 255 — the brightest class of body in our Ethiopian stock, which is what lets the flashes read so cleanly rather than getting lost in a grey background.

Why it costs what it does

1. The colour, overwhelmingly. Coverage, brightness and range of hues. This stone carries one of the two highest rates in our range.
2. A clean bright body that sets the colour off.
3. A sound, well-shaped dome with no crazing and no fractures reaching the surface.
4. Size, last. It multiplies the rate rather than setting it.

The water question

Ethiopian opal is usually hydrophane and absorbs water, after which it can go clear or cloudy and lose its play of colour until it dries. The colour comes back. Dry it slowly at room temperature, never with heat; keep it off during washing, swimming and wudu; and keep oil and perfume away entirely, because those soak into a porous stone and do not evaporate.

Treatment

Not tested. At this rate that deserves stating plainly rather than burying: the specification sheet records the treatment as untested, which is not the same as absent. Smoke treatment is used to darken pale bodies and imitate scarcer dark-bodied opal, and this stone's bright body is not the usual product of it — but the test has not been run. For a stone at this price we would encourage independent laboratory testing, and will arrange it before dispatch if you ask.

Care

Opal rates 5.5 to 6.5 on the Mohs scale. Protective setting, soft dry cloth, no ultrasonic cleaner, no steam, no hot water, and keep it away from harder stones in storage.

More

The opal buying guide covers judging play of colour, the price guide explains the rates, and our authenticity page sets out what we verify. The rest of the range is on the Ethiopian opal page.

Ordering

One piece only. Flat Rs. 500 delivery anywhere in Pakistan by insured, tracked courier, dispatched in one to two working days. Cash on Delivery — open the parcel and look at the stone before you pay — and seven days to return it unused. Dimensions have not been recorded; message us on WhatsApp at +92 308 887 3888 and we will measure it before you order.

This particular stone

This listing is one natural ethiopian opal with a weight of 3.5 Carat. Its price is Rs. 8,750 — roughly Rs. 2,500 for each carat. Origin: Ethiopia. Treatment: treatment not tested. Quote reference GS-000708 when you message us about it. The photographs show this exact stone, so what arrives at your door is the piece you chose on screen.

Between two and six carats is the range most people choose for a gents' ring or a noticeable pendant. Here colour drives the price more than size does, which is why two stones of near-identical weight can be priced very differently.

Whoever you buy ethiopian opal from, make sure of three things: the stone is natural rather than lab-grown, glass or glass-filled; any treatment is stated in writing; and the weight quoted is the weight of the finished stone. We check every ethiopian opal for those three points before it is listed, a certificate is available on request, and because you pay on delivery you can look at the stone — or have it tested — before any money changes hands.

We sell natural stones only and inspect each one before it is listed. Treatment for this stone: Treatment not tested. Certificate available on request. As general background (not a statement about this stone): Solid opal is usually untreated; some opal is smoke- or sugar-treated, and doublets/triplets exist — we sell solid natural opal. Ask us on WhatsApp and we will tell you what we know about this exact stone; independent lab testing is available on request.

A certificate of authenticity is available on request for this stone, and independent laboratory testing can be arranged. Because you pay on delivery, you can also take the stone to a lab of your choice within the 7-day return window. Read more on our authenticity page.