"Rainbow opal" is not a species — it is a description of what the stone does. When several colours fire from the same piece as you move it, people call it a rainbow, and it is the effect that made opal famous. Understanding where those colours come from makes it much easier to judge one stone against another.

The stone

2.50 carats, which is 2.75 ratti. Shape: oval cabochon. Origin: Australia. Rs. 12,500, about Rs. 5,000 per carat, reference GS-000703.

Where the colours come from

Opal is hydrated silica, built from microscopic spheres stacked in an orderly grid. When light passes through that grid it is diffracted — split into its component colours — in exactly the way a soap film or a CD surface splits light. The size of the spheres decides which colour you see: smaller spheres produce blue and violet, larger ones produce orange and red. A stone that shows several colours is one where sphere size varies across the piece.

This also explains the price ladder. Large, uniform spheres are rarer than small ones, so red and orange fire costs more than blue and green. It is geology, not fashion.

Judging a multi-coloured stone

• How many colours, and how strongly. Two bright colours beat five faint ones.
• Coverage. Colour across the whole dome rather than a bright patch surrounded by dead ground.
• Angle range. Tilt it slowly through a wide arc. Good material keeps firing; weaker stone shows one flash and goes quiet.
• Directionality. Some opal only fires from one direction. A stone that works from several directions is more wearable, because a ring is seen from everywhere.

With opal more than any other gem, a video beats a photograph. Ask us on WhatsApp at +92 308 887 3888 and we will send one under moving light before you commit.

Is "rainbow opal" a grade?

No, and you should be slightly wary of anyone who implies it is. There is no formal rainbow grade. What exists is body tone and brightness, both measured on recognised scales, and the colours a stone happens to produce. Our Australian opal buying guide sets those out properly.

Solid and untreated?

Solid, yes — we sell solid natural opal, not doublets or triplets, and the side profile of any opal tells you which it is. On treatment, solid opal is usually untreated, though some is smoke- or sugar-treated to darken the background; we have not tested this stone, so the specification says so rather than claiming it is untreated.

Care

Opal is 5.5 to 6.5 on the Mohs scale and holds water in its structure. Soft damp cloth only, never ultrasonic or steam cleaning, and keep it away from prolonged direct sun and dry heat, which can craze the surface.

Ordering

One piece only. Flat Rs. 500 delivery anywhere in Pakistan, insured and tracked, dispatched in one to two working days. Cash on Delivery, seven days to return it unused. Measurements on request. More in the Australian opal collection.

This particular stone

This listing is one natural australian opal with a weight of 2.5 Carat. Its price is Rs. 12,500 — roughly Rs. 5,000 for each carat. Origin: Australia. Treatment: treatment not tested. Quote reference GS-000703 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 australian 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 australian 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.