A 5.7 carat Ceylon moonstone — 6.26 ratti — at Rs. 3,750, about Rs. 658 per carat.

A first moonstone

Between five and six carat is where most people's first moonstone sits, and there is sense in that. The stone is big enough to read as a proper cabochon in a ring rather than an accent, the total outlay stays modest, and the dome is low enough to survive ordinary wear. If you are buying to find out whether you like moonstone before committing to something larger, this is the sensible weight.

What to look for when the stone arrives

Take it to a single lamp rather than a window. Hold it at arm's length and rock it slowly through about forty-five degrees. The blue should wash across the dome and then disappear as you pass the angle, returning when you tilt back. That movement is adularescence, and it is the test that separates moonstone from the milky quartz and glass sold under its name. A stone that looks evenly cloudy from every angle and never changes is not moonstone.

Why the glow happens

Moonstone is a feldspar that formed as two slightly different feldspars interleaved in layers thinner than a wavelength of light. Light entering the stone scatters off those layers, and the shorter blue wavelengths scatter most, which is why the glow reads blue rather than white. Nothing has been added to the stone to produce it; it is a consequence of how the mineral cooled.

Rate, origin and care

At Rs. 658 per carat this sits around the middle of our collection, where rates run from roughly Rs. 481 to Rs. 776 per carat. Recorded as a Ceylon stone. Clean it with warm water, mild soap and a soft cloth — never an ultrasonic cleaner, steam, bleach or ammonia — and keep it away from harder stones in storage. At 6 to 6.5 on the Mohs scale with good cleavage, it dislikes knocks more than it dislikes dust.

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

This particular stone

This listing is one natural moonstone with a weight of 5.7 Carat. Its price is Rs. 3,750 — roughly Rs. 658 for each carat. Origin: Ceylon (Sri Lanka). Treatment: treatment not tested. Quote reference GS-000408 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.

On the Mohs scale moonstone rates 6 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 moonstone 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 moonstone 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): Moonstone is usually untreated. 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.