Umba sapphire is a unique type of sapphire discovered in 1962 in the Gerevi Hills, north of the Umba River in the Umba Valley of Tanzania. Umba sapphires exhibit coloration not common to sapphires sourced from other parts of the world, and are recovered from the alluvial deposits of the Umba River.
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, copper, or magnesium. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. The only color corundum stone that the term sapphire is not used for is red, which is called a ruby. Pink colored corundum may be either classified as ruby or sapphire depending on locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of very special-purpose solid-state electronics (especially integrated circuits and GaN-based LEDs).
The Umba River is located in northeastern Tanzania in Tanga Region. It rises in Schageiuforest (Shagayu) in the West Usambara Mountains at 2,000 m altitude and flows on the north side of the mountain range to the east. At Lelwa it empties the Mbalamu River, which comes from the extreme north of the Usambara Mountains, and the Mglumi River into the Umba. Just before the Umba flows into the Indian Ocean, it crosses the border to Kenya. The mouth itself marks the most eastern point on the border between Tanzania and Kenya, which was largely made in a straight line to the northwest towards Lake Victoria in the 19th Century. On the upper reaches of the river in the mid-1960s rich deposits of precious stones, including sapphires and spessartine, were discovered. Also on the river is the Umba River Game Reserve, a wildlife reserve that includes along with the Mkomazi Game Reserve, about 2,600 km².
Umba Valley is a geographic area in Tanzania and the world's only source of Umba sapphires.
As of November 2006 [update] , the Tanzanian government prohibits export of these sapphires.
An export in international trade is a good or service produced in one country that is bought by someone in another country. The seller of such goods and services is an exporter; the foreign buyer is an importer.
