Who We Are
Started in 1961 in Rhodesia (now Zimbabwe), Southern Africa, Hilmar began working exclusively with the elite cutting houses in Idar-Oberstein, Germany, supplying gemstone rough from Mozambique, Zambia, and Zimbabwe.
In 1982, Hilmar immigrated to South Africa with his family and opened African Gemstones (the name of the company), supplying fine facet rough mainly to the States. Our first website would follow thereafter. Since then, he has been providing fine facet-grade gemstone rough by mail order to lapidaries all over the world.
Always looking to be ahead of the curve, Hilmar was an early adopter of the internet and developed the first African gemstone website in the early 1990s — no more postcards and paper lists in the mail. Tanganyika Trading, with its own website, was opened in 1994 when we became involved with the gemstones in Tanzania. Both African Gemstones and Tanganyika Trading are now amalgamated and operate under Tanganyika Trading.
Today, we supply rough to tradesmen and women, lapidaries, carvers, and jewellers worldwide, offering individually selected stones and small parcels through the website, as well as larger wholesale parcels direct to gem merchants and cutting houses. Over the years, our sources have expanded far beyond the original three countries we started with more than 50 years ago. We now obtain rough from Mozambique, Namibia, Malawi, Tanzania, Nigeria, Kenya, Zambia, Madagascar, Brazil, Bolivia, Pakistan, Zimbabwe, and many others — and we ship to even more countries around the world.
With an eye towards preserving the art of lapidary and supporting independent cutters and cutting houses alike, we strive to provide only high-clarity facet-grade rough. We aim to disclose as much information as possible about every stone, including origin, treatments, colour, and clarity, while providing honest, personal customer service. We cannot promise perfection, but we always try to make every transaction and interaction smooth, straightforward, and pleasant.
About Us
Hilmar Bosch – Founder
Of Dutch nationality, I was born in Nairobi, Kenya, and spent my early years travelling across Africa with my parents. After completing my education in Harare, Zimbabwe (then Rhodesia), I began studying geology at university but soon realised my true calling was gemstones. In 1963, I left to pursue gemmology full-time, earning my Fellowship Diploma from the Gemmological Association of Great Britain.
I went on to establish and teach the first Gemmology and Gemstone Cutting courses at Harare Polytechnic, while running our jewellery and gem-cutting factory. Over the decades, I built strong relationships with German cutting houses in Idar-Oberstein, who purchased our tourmaline, topaz, aquamarine, and garnet rough, while bulk materials like agate, carnelian, and fossilised wood found ready markets in the USA.
In 1982, following political unrest in Zimbabwe, I relocated to South Africa and launched African Gemstones, later founding Tanganyika Trading in 1994. Both businesses have since been consolidated under one banner — Tanganyika Trading, now found at: tanganyikatrading.com
Michael Howard Lewis – Next Generation
Born and raised in Zimbabwe, Mike’s earliest memories were in the African bush, spending time with his family on camping and hunting trips in places such as the Zambezi Valley. Growing up surrounded by the landscapes and wildlife of Southern Africa helped shape his lifelong appreciation for nature, adventure, and the natural treasures of the continent.
After completing his schooling in Harare, Zimbabwe, Mike went on to study towards a Bachelor of Commerce in Marketing in Cape Town, South Africa. While still at school, Mike first dabbled in gemstones, making all the usual beginner mistakes that ultimately sparked a deeper passion for the trade.
He began his gemmological studies with an introductory course through GEM-A before enrolling at the German Gemmological Association (DGemG) in Idar-Oberstein, Germany, in 2015, earning the title F.G.G. (Fellow of the German Gemmological Association).
In 2024, Mike completed the Graduate Gemologist (G.G.) program through GIA in Carlsbad, California, USA and Bangkok, Thailand. He has also studied through the Harry Oppenheimer Diamond Training School in South Africa.
Now based in London, UK, Mike has worked within the gem and jewellery trade and joins Tanganyika Trading under Hilmar’s mentorship, helping carry the legacy forward with integrity, enthusiasm, and a fresh perspective.
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