A 3.3 carat Ethiopian opal — 3.63 ratti — at Rs. 8,250, about Rs. 2,500 per carat.

What "rainbow" means here, measured

The word is used loosely in the opal trade, so here is the basis for it. Play-of-colour on this stone covers 8% of the face and spans eight distinct hue bands out of the twelve a full circle is divided into — greens, oranges and a 16% blue share, which is well above the typical figure for white-body material. It is a broad spread rather than one dominant flash colour, which is what the name is describing.

Breadth of colour is judged separately from brightness and from pattern, and it is the quality most visible to a casual eye. A stone flashing a single green is more easily matched to a setting; a stone flashing across eight bands changes character as the hand turns, which is the thing people actually mean when they say an opal is alive.

Setting an opal in a ring

Bezel, not claws. Opal is 5.5 to 6.5 on the Mohs scale and the softest gem in common ring use, so it wants a continuous rim protecting its girdle rather than four points of contact. Ask the setter to work cold — opal holds water in its structure and heat is its worst enemy. And set it low; every millimetre of height is another knock.

Ethiopian opal is usually hydrophane

That means porous: it can absorb water, turn temporarily transparent and lose its play-of-colour until it dries out again over hours or days. Harmless in itself, but it means no soaking, no swimming, and real care with oils, soaps and anything coloured, which a porous stone may take up permanently. Take the ring off before washing up.

Body tone

Brightness measures 200 out of 255 — a light body with no dark regions anywhere on the stone. It was previously described as a black opal with a dark body colour, which it is not. Black opal carries a genuinely dark body and sells for many times the price of white material.

Treatment has not been tested on this stone, which we record rather than calling it untreated. Dimensions and clarity are not recorded yet; ask and we will measure.

This particular stone

This listing is one natural ethiopian opal with a weight of 3.3 Carat. Its price is Rs. 8,250 — roughly Rs. 2,500 for each carat. Origin: Ethiopia. Treatment: treatment not tested. Quote reference GS-000720 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.