6th February 2012
An extract taken from the article entitled “Potential for Modernization of Small Scale Gemstone Miners – the Case of the Tsavorite Mines in Southeast Kenya” written by Dr Cedric Simonet and published in the ICA Quarterly publication “In Color”. This extract is republished here with the kind permission of Dr Cedric Simonet..
Gemstone rich Kenya is one of the leading producers of Tsavorite. The green gemstone is mined in several parts of the country, although most mines are located in the Southeast Kenya gemstone belt, next to Tsavo National park, that gave its name to the gemstone. Since the late 1960’s, tens of Tsavorite occurrences have been discovered along the 200 km long belt, and developed to a smaller or greater extent.
In most cases, after a short open pit phase, mining of Tsavorite involves underground methods. Mining is mostly done manually and rarely supported with basic mining equipment, such as compressors and jackhammers. Explosives are rarely used both for fear of damaging the gems, and for lack of technical knowledge in mining and blasting methods. Hoisting equipment is absent. Most Tsavorite mines are licensed by the government, under Mining Location titles (renewable annually) and are therefore operated in accordance with the Mining Act.
The great difficulty of Tsavorite mining is that it occurs in randomly located pockets or “potatoes” within a broader mineralized zone. The mineralized zone dips at an angle of 30 to 70 degrees. Typically, the strategy of small scale miners is to attempt to predict the location of the next pocket through experience and intuition, and to reach such a pocket as quickly and directly as possible. Because the pockets are scattered, this leads to an underground architecture consisting of tortuous and narrow tunnels. Over 99.9 percent of the material excavated from the mine is rock waste, and the complicated shape of the tunnels greatly slows down the speed at which the waste can be removed. This in turn, slows the daily advance rate and therefore pushes back the time when the next pocket will be hit.
As a result, production from tsavorite mines is erratic and unpredictable. This in turn has consequences on the tsavorite market. A low and unpredictable production prevents marketing efforts, keeps awareness about tsavorite low (as opposed for example, to Tanzanite) and maintains demand (and prices) at low levels.
Artisanal miner sorting. Miner sorting rough at a prospect called Mbita in Kwale district.
The understanding of Tsavorite’s geology and mode of formationis still in its infancy. It is difficult to know the exact geometry of the mineralization because miners do not keep records of their production. The simple recording of the location of the pockets on a map would help greatly.
Samples of rough Tsavorite. Reproduced from the ICA In Color magazine. Photo by Peter Hupka.
Difficulties also affect exploration activities. Southeast Kenya is a dry part of the country, ubiquitously covered with thick red soil, with little water drainage. Alluvial prospecting through panning of gravel samples of rivers is not possible. Most gemstone deposits have been discovered through visual identification of small gemstone chips on the surface of the soil or sometimes on eroded termite mounds. This method has its limitations since in areas where the laterite soil thickness exceeds two metres, the underlying gemstone deposits may not show any visible sign of their presence at the surface. This is the reason why, since the early 1970’s, no new major gemstone deposit has been found in the Southeast Kenya gemstone belt, although it is very likely that such deposits are actually present. They are just not detectable by traditional prospecting methods and their discovery will require the use of more modern exploration methods.
The Next Step
As part of its Strategic Plan, the Kenya Chamber of Mines is currently trying to facilitate the setup of a major modernization program for Kenyan gemstone miners, with a strong focus on Tsavorite.
This extract has been republished with kind permission of Dr Cedric Simonet, Chairman of Kenya Chamber of Mines. The full article is printed in the ICA Quarterly publication “In Color” and can be read on the ICA website here
Lapigems Gem Company is a full member of Kenya Chamber of Mines and sits in on the Executive Council meetings. It is also a member of the ICA.