Kenya is one of the most significant coloured-gemstone producing nations in East Africa, with deposits stretching across the Mozambique metamorphic belt that runs through the country from the Tanzanian border northward. The country's two best-known contributions to the trade are tsavorite garnet, the chrome- and vanadium-coloured grossular discovered in the late 1960s, and ruby from the John Saul and other deposits in the Tsavo region.

Tsavorite garnet

Tsavorite was identified as a new variety of green grossular garnet by the Scottish geologist Campbell Bridges in the late 1960s, with deposits straddling the Kenyan and Tanzanian sides of the Tsavo region. The stone was promoted by Tiffany & Co. in the 1970s under the name tsavorite, drawn from the surrounding national park. Kenyan tsavorite is mined principally in the Taita-Taveta County around Voi and Mwatate. The colour-causing trace elements are vanadium and, to a lesser extent, chromium, producing greens that range from a cool fresh green at lighter saturations to an intense forest green in larger stones. Production is dominated by small-scale and artisanal operations with intermittent mechanised activity.

Ruby

Kenyan ruby comes principally from the John Saul mine and the surrounding Mangare area. The material is generally of saturated colour but often heavily included, with stones of clean clarity above one carat being scarce. Some Kenyan ruby is heat-treated and a portion is sold in the carving and bead trade rather than as faceted stones. Recent literature in Gems & Gemology has documented trace-element fingerprints distinguishing Kenyan from neighbouring Tanzanian and Mozambican rubies.

Other gem materials

Kenya also produces rhodolite garnet, spessartine and pyrope-spessartine garnet, tourmaline, aquamarine, and a notable amount of star sapphire and corundum of cabochon grade. Sodalite, kyanite, and a range of ornamental stones are also worked. The Lake Magadi region in the Rift Valley yields zeolites and other minerals of mineralogical interest, although these rarely appear in the gem trade.

Trade and certification

Kenya is a participant in the Kimberley Process Certification Scheme, although it is a minor diamond producer at most. Coloured-stone exports flow primarily through Nairobi and through cross-border trade with Tanzania, with significant cutting and polishing taking place in Bangkok, Jaipur, and Hong Kong. Buyers seeking Kenyan-origin stones with confidence should request laboratory reports from a recognised laboratory; Lotus Gemology and the major laboratories in Bangkok and New York are among those that issue origin opinions for East African rubies and tsavorites.