Begin With the Seller, Not the Sparkle

It is easy to fall for a photograph of a stone before you know anything about the person selling it. Resist that. Before you commit to anything expensive, spend ten minutes on the seller themselves. A genuine gemstone dealer or handmade jewellery maker will be happy to tell you who they are, where they work and how to reach them.

Look for a proper business address, a contact method beyond a social media inbox, and some evidence of trading history — reviews, a shop front, a market stall, a workshop. Then send a message with two or three specific questions before you buy. How quickly and how thoroughly they reply tells you a great deal about how they will behave if there is a problem later.

Be wary of pressure. Phrases like "only one available" or "price goes up tomorrow" are sales tactics, not facts. Good stones are not that rare, and there is always another one.

What a Good Photograph Should Show You

Most online gemstone disappointment begins with photography. Gemstones are small, reflective and notoriously difficult to capture honestly. A skilled photographer can make a pale, cloudy stone look like a vivid treasure. So ask for the following before you decide:

• Images taken in daylight, ideally outdoors or near a window, rather than under a ring light or with a filter applied
• A shot against a plain white or grey background, so you can judge the colour without a coloured surface bouncing light back into the stone
• A clear view of size — a ruler, graph paper or a familiar coin beside the stone, because a 6 mm round looks nothing like a 10 mm one
• The stone held in tweezers or resting on a fingertip, showing how it behaves in ordinary light
• A short video with a slow rotation, so you can spot inclusions, dull patches and how the colour shifts as it moves

Remember that your screen is not colour-calibrated, and neither is theirs. Ask the seller to describe the colour in words: "a soft, slightly greyish blue-green, darker at the edges" is far more useful than "stunning teal".

Ask Plainly About Treatments and Origin

Most gemstones on the market have been treated in some way. Heated sapphires and rubies, oiled or resin-filled emeralds, dyed agates, irradiated topaz and fracture-filled stones are all commonplace. These treatments are not automatically a problem — but they must be disclosed before you buy, not discovered afterwards.

Ask directly: "Has this stone been treated in any way, and is the colour natural?" An answer like "it's a natural stone" does not address the question. Lab-grown and synthetic stones are perfectly legitimate in their own right, but they should never be sold as mined material. If a sale seems to hinge on a certificate, ask which independent gemmological laboratory issued it and whether you will receive the original document with the stone.

Judge Cut, Clarity and Durability Together

A beautiful colour means little if the stone is cut so shallowly that it has a large window — a see-through patch in the middle that lets light fall straight out. Ask whether there are inclusions visible to the naked eye, and whether the stone is eye-clean. For a piece of handmade jewellery, durability matters as much as beauty.

Hardness is measured on the Mohs scale. Stones of 7 and above — quartz, garnet, spinel, corundum — are sensible choices for a ring you intend to wear daily. Softer materials such as opal, pearl, fluorite and malachite are happier in earrings, pendants and brooches, where they are less likely to be knocked.

Check the metal too. In the UK, items above certain weights in gold, silver, platinum or palladium should carry a hallmark. "Gold plated" and "gold filled" mean something very different from solid gold, and a listing should say so clearly.

Measurements, Weight and Price Sanity

Carats and millimetres tell different stories. Two stones can weigh the same yet look completely different, because one is cut deep and narrow while the other is broad and shallow. Always ask for the millimetre measurements as well as the carat weight.

Price is your quietest and most reliable warning system. If a three-carat ruby is offered at the price of a modest pair of earrings, something is doing the work: heavy treatment, poor clarity, a different species altogether, or a plain misdescription. Compare a handful of sellers offering similar material before you commit. A wide gap between one price and all the others nearly always has an explanation, and it is rarely a happy one.

Returns, Payment and Keeping a Paper Trail

This is the part that saves you money. Read the returns policy in full before you pay. Under UK distance selling rules, most online purchases come with a short cancellation period — typically 14 days from delivery — but bespoke, resized and personalised pieces are often excluded. If the policy is vague, contradictory or missing altogether, treat that as your answer.

• Confirm in writing whether custom-cut or made-to-order stones can be returned
• Ask who pays return postage, and whether the item must be sent tracked and insured
• Pay by a method that offers buyer protection rather than a direct bank transfer
• Keep the listing description, your messages and the seller's photographs
• Inspect the stone in daylight as soon as it arrives, and raise any mismatch promptly and in writing

Finally, trust your instincts. A seller who welcomes questions, sends honest photographs and writes their policies in plain English is worth paying a little more for. The stone you keep for decades is rarely the one you bought in a hurry.