A 6.15 carat opal — 6.76 ratti — at Rs. 10,880, about Rs. 1,769 per carat. That is the lowest per-carat rate among the stones on this page, and the body is the palest grade of all: brightness measures 200 out of 255.

Why this one is named for its blue

Play-of-colour in opal is almost never evenly spread across the spectrum. Green and orange dominate most white-body material, and blue is the hardest of the three to find in quantity because it sits at the short-wavelength end where the silica spheres have to be smallest and most regular. Measured across its flashes, 19% of this stone's play-of-colour falls in the blue band — the highest of any stone in this group, where the typical figure is 3% to 13%.

The flashes cover 8% of the face and span nine distinct hue bands, so this is not a blue stone with a little green: it is a broad multicolour display that happens to carry unusually strong blue alongside the green.

Where the colour comes from

Opal is hydrated silica — silicon dioxide with water locked into it, anywhere from 3% to 21% by weight. It has no crystal structure. Instead it is built of microscopic silica spheres stacked in a regular grid, and when those spheres are the right size and regularity they diffract light the way a CD surface does, splitting it into spectral colours. Sphere size decides which colour you see: larger spheres give red, smaller give blue. That is why blue-dominant opal is common and red-dominant opal is rare and expensive.

This is a white opal, not a black one

Worth stating plainly, because the terms are often used loosely. Body tone is the background the play-of-colour sits against, and it is graded separately from the colour itself. This stone has a light body — measured at 200 out of 255, with no dark regions at all. Black opal, which carries a dark grey to black body and sells for many times the price, is a different thing entirely. Nothing in this listing is black opal.

Care

Opal is 5.5 to 6.5 on the Mohs scale and contains water, which makes it the most demanding gem in ordinary jewellery. Never an ultrasonic cleaner, never steam, never sudden heat or prolonged dry heat. Wipe it with a soft damp cloth. Take the ring off before washing up or using household chemicals, and store it away from harder stones.

Treatment has not been tested on this stone, and we record that rather than calling it untreated. No documented origin is held for it, so we do not claim one. Dimensions and clarity are not recorded yet — ask us and we will measure.

This particular stone

This listing is one natural opal with a weight of 6.15 Carat. Its price is Rs. 10,880 — roughly Rs. 1,769 for each carat. Treatment: treatment not tested. Quote reference GS-000728 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.

From six carats up a stone becomes the centre of attention. It wants a broader shank or a secure claw setting and suits an occasion ring, a signet or a centre pendant. Clean natural material of this size turns up far less often, and the per-carat rate reflects that.

On the Mohs scale opal rates 5.5 to 6.5. That is middle-of-the-road hardness: comfortable in pendants and earrings, and in rings worn with some care. Store it apart from harder stones so it does not pick up scratches, and wipe it with a damp cloth rather than scrubbing.

Whoever you buy 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 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.