Almost all opal is cut as an oval cabochon, and unlike most shape choices this one is not about fashion. It follows from what opal is and how the colour works, and knowing why makes it easier to judge whether a particular stone has been cut well.

The stone

2.70 carats, which is 2.97 ratti. Shape: oval — recorded for this individual stone. Origin: Australia. Rs. 13,500, about Rs. 5,000 per carat, reference GS-000607.

Why opal is domed, not faceted

In a faceted gem the sparkle comes from light bouncing off internal facets. In opal the colour comes from inside the material itself, diffracted by microscopic silica spheres. Facets would do nothing for it and would waste material. A smooth dome does two useful things instead: it presents the colour from many angles at once, and it gathers light into the stone rather than scattering it.

The oval outline follows for practical reasons. It wastes less of the rough than a round, it has no corners to chip on a soft stone, and it sits along the finger comfortably.

What a well-cut opal cabochon looks like

• An even dome. Run your eye along the profile. It should curve smoothly with no flat spot in the middle — a flat top usually means the cutter was saving weight at the cost of the colour.
• A symmetrical outline. Fold the oval in half in your mind, both ways; both halves should mirror. A lopsided outline forces a custom mount.
• Enough height. A very shallow cabochon is fragile at the edges and harder to bezel securely.
• A clean surface. No sand pockets, pits or scratches on the dome. Opal is soft, so a careless polish shows.
• A flat, even base. It has to sit properly in the setting.

Setting an oval cabochon

Oval cabochon mounts are stock at every jeweller in Pakistan, which keeps the cost of setting down and makes a future reset straightforward. For opal, specify a bezel rather than claws — the rim protects the edge of a soft stone — and keep the setting low. Exact length and width have not been recorded for this piece, so ask us on WhatsApp at +92 308 887 3888 and we will measure it before your jeweller orders a mount.

Solid opal and treatment

We sell solid natural opal, not doublets or triplets — check any opal edge-on for a straight glue line. Solid opal is usually untreated, though some is smoke- or sugar-treated to darken the background; this stone has not been tested and the specification says so. A certificate of authenticity comes on request.

Care

Opal is 5.5 to 6.5 on the Mohs scale and holds water. Soft damp cloth only, never ultrasonic or steam, and keep it away from prolonged sun and dry heat.

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. Compare shapes and sizes in the Australian opal collection.

This particular stone

This listing is one natural australian opal with a weight of 2.7 Carat. Its price is Rs. 13,500 — roughly Rs. 5,000 for each carat. Origin: Australia. Treatment: treatment not tested. Quote reference GS-000607 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.