Loose Tanzanites

About tanzanite

Tanzanite is found in only one place in the world, near Mount Kilimanjaro in Tanzania. Its violet-blue changes with the light. At 6 to 6.5 on the Mohs scale it is softer than sapphire, so it suits earrings, pendants or a ring with a protective setting. Almost all tanzanite is heated. It is a birthstone for December.

How to choose a coloured gemstone

Colour comes first. The finest stones have a rich, even colour that is neither too pale nor so dark it looks black indoors. Look at the photo and the video where there is one: a well-cut stone shows its colour across the whole face, with few dull or see-through patches.

Size next. Coloured stones weigh more for their size than diamonds, and many are cut deep to hold their colour, so two stones of the same carat weight can look quite different. Check the measurements in millimetres: for a ring, 6 to 8 mm across suits most hands.

Then clarity. Almost every natural coloured stone has small inclusions; they are part of what makes it natural. What matters is that they don't spoil its brightness. Emeralds are the exception to the rule: visible inclusions are expected and accepted.

Treatments, explained

Most coloured gemstones are treated in some way, and that is normal. Heating, the most common, brings out colour and clarity and is permanent. Emeralds are oiled to make their natural fissures show less. Blue topaz is irradiated to give its colour.

Some treatments change the value much more: beryllium diffusion (used for many orange and padparadscha-coloured sapphires) and glass filling (used for some rubies). We show the treatment of every stone on its page and explain what it means, so you always know what you are buying.

Certificates

Many of our stones come with a report from an independent gem laboratory such as GRS, Gübelin, SSEF, AGL or GIA. The report confirms the stone is natural, names it, records any treatment and, for finer stones, its country of origin. Tick "Certified only" to see just those stones.

Set your gemstone in a ring

Found a stone you love? We can set it in any of our ring designs, from a classic claw solitaire to a diamond halo or three-stone ring, or design a ring around it. Every ring is made to order in our Cotswolds workshop, usually in 3 to 4 weeks, and hallmarked. Comparethediamond.com is part of 247 Diamonds, a family jeweller since 1969 and a member of the National Association of Jewellers.

Try the shapes and settings in Ring Maker, or ask us on WhatsApp for a quote.

Looking after a coloured gemstone

Sapphire and ruby need very little care: warm soapy water and a soft brush keep them bright. Softer stones such as emerald, tanzanite and topaz should be kept away from ultrasonic cleaners, steam and sudden heat, and taken off for gardening, the gym or heavy work.

Shop by gemstone

• Loose sapphires
• Loose rubies
• Loose emeralds
• Loose tanzanites
• Loose aquamarines
• Loose morganites
• Loose tourmalines
• Loose garnets
• Loose topaz
• Loose amethysts