Tsavorite or tsavolite is a variety of the

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. Garnet minerals, while sharing similar physical and crystallographic properties, exhibit a wide range of chemical compositions, de ...

group species grossular, a

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

garnet with the formula Ca₃ Al₂ Si₃ O₁₂. Trace amounts of vanadium or

chromium Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium ...

provide the green color. In 1967, British gem prospector and geologist Campbell R. Bridges discovered a deposit of green grossular in the mountains of Simanjiro District of Manyara Region of north-east

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

in a place called Lemshuko, away from Komolo, the first village. The specimens he found were of very intense color and of high transparency. The find interested the gem trade, and attempts were made to export the stones, but the Tanzanian government did not provide permits. Believing that the deposit was a part of a larger geological structure extending possibly into

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

, Bridges began prospecting in that nation. He was successful a second time in 1971, when he found the mineral variety there, and was granted a permit to mine the deposit. The gemstone was known only to mineral specialists until 1974, when Tiffany and Co launched a marketing campaign which brought broader recognition of the stone. Bridges was murdered in 2009 when a mob attacked him and his son on their property in Tsavo East National Park. It is believed that the attack was connected to a three-year dispute over access and control of Bridges' gemstone mines. The name ''tsavorite'' was proposed by Tiffany and Co president Henry Platt in honor of Tsavo East National Park in

. Apart from this source and the first discovered locality in Manyara,

, it is also found in Toliara (Tuléar) Province,

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

. Small deposits of gem grade material have been found in Pakistan and Queen Maud Land, Antarctica. No other occurrences of gem material have yet been discovered. Rare in gem-quality over several carats (1 carat = 200 mg), tsavorite has been found in larger sizes. In late 2006, a crystal was discovered. It yielded an oval mixed-cut 325 carat (65 g) stone, one of the largest, if not ''the'' largest, faceted tsavorites in the world. A crystal that yielded a oval mixed-cut gem was also uncovered in early 2006. The Lion of Merelani is a square cushion cut tsavorite that weighs 116.76 carats and has 177 facets. It is on display at the

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums, Education center, education and Research institute, research centers, created by the Federal government of the United States, U.S. government "for the increase a ...

. Tsavorite formed in a

Neoproterozoic The Neoproterozoic Era is the last of the three geologic eras of the Proterozoic geologic eon, eon, spanning from 1 billion to 538.8 million years ago, and is the last era of the Precambrian "supereon". It is preceded by the Mesoproterozoic era an ...

metamorphic event which involved extensive folding and refolding of rock. This resulted in a wide range of inclusions forming within most Tsavorite crystals. These inclusions are strong identifying features in Tsavorite.

References

External links

Daily Telegraph obituary for Campbell R. Bridges
{{Gemstone Calcium minerals Aluminium minerals Garnet gemstones