Sunday, June 11, 2017

Sapphire Mines In Africa

Tanzania obtains much of its gem wealth from a geological feature known as the Mozambique Orogenic Belt, which contains one of the richest gem loads on earth.  The Belt runs in a north-south direction through the eastern part of the country and it is up to 300 kilometers wide in places.  The rocks in this mountain belt have undergone significant tectonism and metamorphism, which has created a multitude of gemstones, including sapphires.The majority of the sapphires from Tanzania are found in three locales: the Umba River Valley in the north, and Tunduru and Songea in the south.


The gem gravel of the Umba River Valley has been a major source of fancy sapphires for at least half a century.  The area yields sapphires in all colors of the rainbow, including highly valued padparadscha and rare color-change sapphires.  The finds are usually facetable grade and some of the stones are sizeable.

Songea, the most productive sapphire mining region in Tanzania, has been worked since the mid 1990s.  Most of the stones tend to be blue.  A majority of the finds go to Thailand for treatment before they reach the market.  Although two mechanized mining companies have been working the area in recent years, most of the mining activity is small scale. Although sapphire production levels have varied over the years, Tanzania is considered to have tremendous future potential.   The Tanzanian government is actively involved in building a sustainable future for its promising gemstone industry.

Sapphires were first found in Kenya in 1936 at Kinyiki Hill where crystals up to one meter long were discovered. Kenya holds enormous potential as a future source of sapphires with their access to the Mozambique Orogenic Belt, which bisects the country in a north-south direction.While the ruby and tsavorite deposits of Kenya are well known, sapphires are a relatively new and unexplored resource.  To date, the country’s sapphire wealth has not been completely inventoried and new deposits are continually being discovered in many different parts of the country. Today, promising mining locations include the Baringo district, which produces pink sapphires; Garba Tula, which produces blue,green, and yellow sapphires; and Turkana, which is known for its blue sapphires.


Nigeria is the most important producer of gems in West Africa.  Nigeria produces aquamarine, emerald, amethyst, garnet, tourmaline, topaz, and zircon among other gemstones.Sapphires have been mined in the central part of Nigeria for about 20 to 30 years.  The government of Nigeria is seeking to expand its mining enterprise with the aid of international loans and investment.  Although the extent of the deposits in Nigeria has yet to be evaluated, the prospects for the future look promising.


Small-scale mining operations are reported in the States of Borno, Kaduna, Taraba, and Bauchi.  There, the sapphires are retrieved from secondary deposits of weathered alkali basalts.  The yields are primarily dark blues and greens.  Although the clarity can be excellent, the stones are mostly small in size.  Many of the sapphires are heat treated to improve their color.

For the last ten years, Madagascar has experienced a sapphire rush. Although sapphire deposits are known to exist all over the country, mining was banned in the northern portion of the island in the 1990s in an effort to protect indigenous species.  In the south however, new discoveries of quality sapphires caused a massive migration to the area.

Many of the gem deposits in Madagascar have not yet been inventoried.  This is particularly true of Ilakaka, which is rumored to be the world’s largest sapphire deposit of real economic value.Sapphire deposits in the north come from alluvial deposits of weathered basaltic rocks, while those in the south have metamorphic origins.  Mechanized mining is difficult given the scattered nature of the deposits and the high costs involved.  Miners manually excavate pits 15 feet wide and up to 80 feet deep.  Gravel is hauled from the pits and washed in nearby rivers.

The sapphires of Madagascar are usually blue, but colorless, pink, purple,orange, yellow, and green stones are also found.  Padparadscha and color-change sapphires are also mined on the island.