A round ten carats and a round Rs. 9,000: the arithmetic on this blue topaz is about as easy as it gets. Divide one by the other and you arrive at about Rs. 900 per carat, which is a useful yardstick when you set it against the other stones in the shop.

Blue topaz on the market gets its colour from irradiation and heating. Dealers consider that standard practice, and the resulting blue is stable in daylight and heat. We would rather you hear that from us than assume otherwise, and we are glad to say what we know about this particular stone, with independent lab testing available if you prefer it.

Ten carats is a large stone for topaz, and on a hand it reads as a clear patch of blue rather than a shimmer. With a Mohs hardness of 8 it will cope with ordinary wear, but give it a setting with some metal around the edges, since a hard blow to a corner can crack topaz along its cleavage.

The reference for this piece is GS-BL-0005. Others of similar weight sit in the blue topaz category, and orders go out with Cash on Delivery, so you can look the stone over before you pay.

Order with Cash on Delivery anywhere in Pakistan: open the parcel, check the stone, then pay. If it is not right for you, you have 7 days to return it. Before you choose, read our blue topaz guide.

This particular stone

This listing is one natural blue topaz with a weight of 10 Carat. Its price is Rs. 9,000 — roughly Rs. 900 for each carat. Treatment: treatment not tested. Quote reference GS-BL-0005 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 blue topaz rates 8. Few materials will scratch it, so it copes well with everyday ring wear. A soak in warm water with a drop of mild soap and a soft brush keeps it bright; skip the ultrasonic cleaner if inclusions reach the surface.

Whoever you buy blue topaz 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 blue topaz 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): Blue topaz gets its blue colour from irradiation and heating — this is standard for the stone and the colour is stable. 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.