Gemstone Mining in Umba, Tanzania: Sapphires and Garnets

Tanzania has given me some of the most memorable field experience of my gemmological career. In the Umba region, north of Tanga, I spent several days working alongside local miners searching for sapphires and garnets an experience that gave me a much deeper understanding of how difficult it is to find usable gemstone material at source.

Reaching the mining areas was an experience in itself. Some of the routes were remote, rough and genuinely challenging, which reinforced just how far removed gemstone mining can be from the polished world of jewellery. Accessing these locations gave me valuable context for the conditions in which many gemstones begin their journey.

Umba lies in north-eastern Tanzania, close to the Kenyan border, and is one of the country’s best-known gemstone-producing regions. Reaching the area takes time, but that remoteness is part of what makes the experience so revealing: this is where gemstones are encountered in the context of geology, mining and local livelihoods rather than as finished objects in a showroom.

Working with local miners was essential. Their knowledge of the ground, mining techniques and ability to recognise promising material were invaluable, and employing them directly also supported local livelihoods. Their stamina was extraordinary, they could dig at a pace I could never match. My role came later, when the material was ready to be sorted and examined for potential gemstones.

Most people recognise sapphires once they have been cut and polished, but rough sapphire can look surprisingly ordinary. In the field, there is no polished surface, perfect symmetry or jewellery setting to help you. You are looking for subtle clues in colour, crystal form, texture and the way the material interacts with light.

Would you recognise a sapphire before it had been cut and polished? I found that far more difficult than I expected. Garnets were easier to spot, particularly the colourful rhodolite and Malaya garnets, but it took time before I became confident identifying rough sapphire amongst the surrounding material.

I eventually came away with around fifty to sixty garnets, black tourmaline and numerous sapphires of different sizes. None of the sapphires were transparent or of usable gem quality. Far from being a failure, that was one of the most valuable lessons of the experience: finding a gemstone is not the same as finding a good gemstone. Exceptional material really is rare.

Masai Miners - artisinal mining for Tanzania's rare gemstones

The miners generally worked in teams of two or three

Miners sang and danced as they walked back from the mine

The miners took it in turns to dig and sift

Every day the miners paired up with a different miner

Sometimes the miners worked in teams of three

Mining for garnets and sapphires in Umba

Initially the miners took it in terms to dig

Judith is a Masai miner

I had two different miners for every dig

I also wrote about my Tanzania field experience for the World Gem Foundation’s Gemmology Today magazine, published in September 2023.

If you are interested in the practical side of buying gemstones at source, you may also find this useful: Can You Legally Buy and Export Gemstones from Tanzania?

Meet Kim Rix in September's Gemmology Today

Kim Rix, GG GIA

Gemstone Detective

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