Sierra Leone

Geological Survey and Mines Division
Ministry of Mineral Resources
NewEngland, Freetown
Phone: +232-22 240 740/22 240 382/ 22 240 688
Fax: +232-22 241 936

CIA Factbook

Source: CIA Factbook



Sierra Leone is divisible into two major tectonostratigraphic units. The eastern division, known as the Kenema-Man Domain, is part of the Precambrian West African Craton and consists of crystalline basement comprising high-grade metamorphic rocks, granitic gneisses, greenstone belts and less frequent Banded Ironstone Formation lithologies. The western unit contains the various elements of an orogenic belt named the Rokelides that was deformed during the Pan-African tectonothermal event, about 550-560 Ma ago, and at least in part comprising reworked units of the Kenema-Man Domain. The two units are regionally separated by a major NW-SE east trending thrust fault zone. The 20-40 km wide coastal strip is made up of Pleistocene to Recent sediments.


Sierra Leone is rich in minerals and historically has been strongly dependent on mining, especially of gem-quality alluvial diamonds, for its economic base and foreign currency earnings. Other mineral commodities that are produced include bauxite, rutile, ilmenite and gold. In the past the mining industry has generated up to 18% of the country’s GDP and 90% of its export earnings. Sierra Leone is among the top 10 gem-quality diamond producing nations in the world. Gem quality stones account for approximately 60% of the country’s production. Though rich in diamonds, it has continually struggled to manage their exploitation and export. Total diamond output from Sierra Leone decreased by 38.5 per cent in 2008 and the country slipped in the rankings from 8th to 10th place (equivalent to 0.39%) within Africa. The mining and export of bauxite and titaniferous heavy mineral sands in Sierra Leone resumed in 2005. The country was the second largest bauxite producer in Africa, after Guinea, and in 2008 accounted for 5% of total output. Sierra Leone was the third largest world producer of rutile after Australia and South Africa, and accounted for 15.61% of total output. It has some of the world's largest reserves of rutile and is ranked fourth in terms of its reserve base. Ilmenite co-production was relatively modest by comparison but the country was ranked fourth in Africa in 2008. Sierra Leone is a relatively small producer of gold. The marked increase in the world market price has led to an expansion of alluvial gold mining activities into new areas of the country. Nevertheless, gold production declined by 7.8 per cent in 2008 after its peak in 2007.
Sierra Leone is widely recognized as a highly prospective target for mining activities. The return to political stability in Sierra Leone coupled with positive global developments in the mining sector now offers the ideal opportunity to rejuvenate the domestic mining sector. Key developments that have significantly improved the prospects of the country’s mining sector include:
  • The successful implementation of an IMF-supported economic reform programme, which has established a sound macroeconomic environment;
  • The introduction of the certificate of origin scheme and implementation of the subsequent Kimberley Process, which has facilitated a rapid return of diamond exports to official channels; and
  • Strong global demand for minerals, underpinned by rapid growth in emerging economies, which has fuelled an investment revival boom in the mining sector. Of particular interest to Sierra Leone is the dominance of junior exploration companies in this revival, since they will be most likely to underpin the exploration investments needed to establish Sierra Leone’s mineral potential, and the increasing appetite of major mining companies to make large investments in what are perceived high-risk, emerging economies.

Maps and images

(Source: Ministry of Mineral Resources)

The Republic of Sierra Leone is located on the West Coast of Africa, between latitudes 7 and 10 north and longitudes 10.5 and 13 west. The Republic of Guinea is to the north and northeast; Liberia is to the east and southeast, and the Atlantic Ocean on the west and south. It has 300 miles of coastline.
From an approximate 70-mile coastal belt of low-lying land, the country rises to a mountain plateau near the eastern frontier rising 4000 to 6000 feet with a rich timber forest region. The Western Area encompasses the Sierra Leone Peninsula, on which the capital and main commercial centre of Freetown stands; is 24 miles long and 10 miles wide.

A mountainous promontory, it rises in places to 300 feet above sea level - one of the few parts of the West African Coast where there is high land so near the sea. Where the lush green forest spills down hillsides to meet the most beautiful white sandy beaches along the Atlantic Ocean.

This 27,925 square mile (73,326 sq km) country has a population of approximately 4.5 million people. Sierra Leone is divided into four main Provinces, West, North, East and South. There are twelve Districts in the entire country.

Most of the country is underlain by rocks of Precambrian age (Archaean and Proterozoic) with a coastal strip about 50 km in width comprising marine and estuarine sediments of Tertiary and Quaternary to recent age. The Precambrian (mainly Archaean) outcrops over about 75% of the country and typically comprises granite-greenstone terrain. It represents parts of ancient continental nuclei located on the edge of the West African Craton. Regional reconnaissance mapping indicates that the Archaean basement can be subdivided into infracrustal rocks (gneisses and granitoids); supracrustal rocks (containing greenstone belts); and basic and ultrabasic igneous intrusions. The infracrustal gneisses and granitoids were formed and reworked during two major orogenic cycles, an older Leonean episode (~2,950-3,200 Ma) and a younger Liberian episode (~2700 Ma).

The Leonean orogenic episode commenced with the intrusion of a basic igneous suite (the Pre-Leonean amphibolites) and by the formation of a greenstone belt represented by the Loko Group which is now deeply eroded. The Loko Group comprises amphibolites, silimanite quartzites and ironstones. It appears to have formed on a gneiss/granitoid basement in which several granitoid bodies related to an earlier plutonicorogenic episode have been distinguished mainly in the northern part of the country. Only the main deformational phase of the Leonean orogenic episode which resulted in folds and fabrics trending east-west has been distinguished. Minor gold and cassiterite mineralization associated with portions of the Loko Group is probably related to a late Leonean granitisation event which accompanied the formation of major shear zones in the craton.

Other volcano-sedimentary sequences are preserved within the granites, gneisses and migmatites. Highly folded greenstone belts predominate in the north and central Sierra Leone. In the southeast, the metamorphic facies increases, first with the Kambui Schists and finally with the Mano-Moa Granulites. Greenstone belts of the Kambui Supergroup are believed to have been deposited upon a post-Leonean basement and accompanies by basic to ultrabasic intrusives. The Kambui Supergroup includes most of the schist belts exposed in the Sula Mountains and the Kangari, Kambui, Nimini and Gori Hills; the Marampa Group; and the two small greenstone belts of Serekolia and Sankarama in the northeast. These greenstone belts comprise a lower volcanic unit composed of ultrabasic lavas and basic lavas with pillow layers, overlain by a sedimentary unit comprising tuffs, pelitic and psammitic sediments, with conglomerate layers and ironstone bands. The greenstone belts are the principal hosts of the gold mineralisation of the country.

Other associated mineral deposits include molybdenite, columbite-tantalite and chromite. The Marampa Group, bounded on its eastern margin by a tectonic contact, is important for its iron-ore deposits and forms the upper part of the Kambui Group. Late Liberian granitoids, marginal to, and within, the Kambui Supergroup, are associated with important zones of shearing and deformation where gold, sulphide and molybdenite mineralisation has been concentrated. 

The Rokel-Kasila Zone bounds the main part of the West African Craton on its west and southwestern margin in Sierra Leone, and appears to form part of a north-south orogenic belt. Within this belt, the Marampa Group appears to represent some of the oldest rocks. The Kasila Group, also considered to be part of the Kambui Supergroup, comprises a high-grade series of granulites, consisting of garnet, hypersthene and hornblende gneisses, quartzites and associated migmatites. Where eroded, signi_ cant secondary deposition of titanium minerals have formed from this unit. The Kasila Group also contains bauxite.

A late Precambrian to Cambrian sedimentary and volcanic assemblage, the Rokel River Group, was deposited unconformably on a basement complex. Deposition was probably in a fault-bounded basin of the intracratonic type along the line of the Rokel-Kasila Group following the formation of the tectonic zone at the end of the Liberian or during the Eburnean Orogeny. The Rokel River Group and the Kasila Group to the west were deformed during the Rokelide orogenic episode (~550 Ma). Deformation increased in intensity westwards.

The Saionya Scarp Group forms a small ingression into Sierra Leone in the northwest of the country, and is composed of horizontally-bedded arkoses, grits and shales with intruded dolerite sills. The group appears to belong to that part of the Gres Horizontaux of Guinea which has been classi_ ed as Ordovician, based on the discovery of the graptolites Monograptus riccartonensis and Monograptus priodon in shales near Telimele.

In Sierra Leone, the Saionya Scarp Group rests on The Rokel River Group.

Dolerite intrusions are common as dykes trending mainly east-west within the basement complex, and as extensive sills above the Rokel River Group. Kimberlite dykes and pipes follow a similar pattern in the east of the country and could also be present in the north and west.

The Freetown igneous complex forms an intrusive body on the coast, with arcuate outcrop concave towards the west. It is composed of a layered complex of gabbro, norite, troctolite and anorthosite. Platinum occurs in the gravels of many of the streams that cut the outcrops of anorthosite and anorthositic gabbro in the noritic gabbro complex of the Freetown Peninsula. The relation of this complex with the other units is obscured by the coastal veneer of Tertiary sediments of the Bullom Group which lies unconformably on the basement. Tertiary and more recent weathering has led to lateritisation across a large part of Sierra Leone, affecting mainly the greenstone belts and the extensive dolerite intrusions. The bauxite deposits formed within the Kasila Group are a result of this weathering process.

Facts in Brief
  • Sierra Leone’s primary mineral resources are diamonds, rutile, bauxite, gold and iron ore. The mineral sector in Sierra Leone is made up of three sub-sectors: a) large-scale production of non-precious minerals – rutile and bauxite; b) large scale production of precious minerals – diamonds; and c) artisanal and small-scale production of precious minerals – mainly diamonds, and to a much lesser extent, gold.
  • The mining sector contributed around 20% of GDP and fiscal revenues equal to 8% of GDP until the closure of the bauxite and rutile operations in 1995. It continues to supply 90% of exports due to the thriving artisanal diamond component. Mining and quarrying employ about 14 percent of the total labour force.
  • The value of minerals exports reached more than $140 million in 2007, thereby returning, at least in nominal terms, to the previous peak achieved in 1991. With the prospect of new modern gold and diamond mines opening in the next 3-5 years, it is estimated that annual mineral export revenues could exceed $370 million.
Recent History

Prior to the civil war, Sierra Leone had established an active mining sector built upon significant exports of diamonds, rutile and bauxite. Although relatively modest by global standards, the sector was significant in terms of the country’s population and GDP. It underpinned much of the country’s formal economic activity, contributing 20% of GDP, as much as 15% of fiscal revenues, and accounting for over 90% of exports. Mining and quarrying provided a livelihood for over 250,000 people, and employed about 14% of the total direct and indirect labour force. Despite the sector operating at only a fraction of its potential, its contribution was significant enough to qualify Sierra Leone as a resource-rich country.

The Impact of Hostilities

Sierra Leone slipped off the investment radar for most major mining companies well before the outbreak of hostilities in 1991. The effective nationalization of the diamond industry and increasing political instability relegated the country to, at best, a speculative exploration target. Although the established rutile and bauxite operations continued to play an important economic role, large-scale exploration activities effectively came to a stand-still more than 20 years ago. As the sector’s economic importance declined, so too did the capacity of key Government departments to regulate sector developments.

Recognising the need to establish an enabling environment for attracting new investment into mineral exploration and development, new mining policies were adopted in 1995 and 1998. The fact that these policies coincided with the forced closure of two foreign-owned mines meat, however, that their impacts were neglible. Without a return to peaceful times and greater political stability, credible international investors would not consider Sierra Leone as a potential exploration target.

The End of Hostilities

The end of hostilities marked the start of a strong economic recovery. Double-digit economic growth during 2001 and 2002 led to a significant period of economic expansion. Real GDP growth averaged nearly 8 per cent per annum for the period 2003 to 2006 and is forecast by the International Monetary Fund to continue at over 6 per cent per annum in the medium-term.

The mining sector has played an instrumental role in Sierra Leone’s nascent economic recovery. In four of the last five years, the rate of growth recorded in the mining sector has exceeded that in the remainder of the economy. The resurgence of the mining sector has been two-fold. First, the Government – with external support – has had considerable success in increasing the proportion of diamonds mined that pass through official channels. Official exports have increased to 582,000 carats in 2006, with 84 per cent of this amount being mined by artisanal and small-scale miners. The U.S. dollar value per carat has also increased significantly, suggesting that larger, more valuable diamonds are increasingly returning to official export channels.

Second, three mechanized mines have been reactivated. The country’s first Kimberlite diamond mine has been operating since 2004 and is progressively expanding production. Also, both of the rutile and bauxite deposits that were developed before the war are once again being mined. The rutile mine is on-track to return to pre-war production levels this year, and plans are in place to expand operations further. The mine’s owners have also acquired the rights to mine bauxite at Moyamba and successfully produced over 1 million tons in 2006.

In 2006, the estimated value of official mineral exports reached a record of US$176 million. This represented around 91 per cent of total export earnings. Faced with a large current account deficit, which creates reliance on foreign aid to fund Sierra Leone’s import needs, the rapid increase in mineral exports has provided a much-needed injection of foreign exchange.

As a result of the many channels through which revenue streams flow from the mining sector to Government, it is difficult to accurately determine the sector’s contribution to public revenues. It is clear though that it fell significantly as diamond smuggling increased and the formal mining sector collapsed. The World Bank estimates that having provided 8 per cent of Government revenues immediately prior to the civil war, the sector’s fiscal contribution plummeted to only 1 per cent of total Government revenues by the end of the hostilities. Despite the strong rebound of the mining sector in recent years, its contribution to public revenues remains weak, in part reflecting significant continued avoidance of official export channels. It is estimated that the sector contributed around 29 billion Leones to public revenue in 2006, which is equivalent to around 3.1 per cent of total public revenues.

The resumption of rutile and bauxite mining has re-established the two mines as two of the largest private sector employers in Sierra Leone. Prior to their closure these mines employed over 3,000 workers. The vast majority of income-earning opportunities generated by the mining sector, however, are in artisanal diamond mining. The World Bank has estimated that up to 40,000 people are directly engaged in mining for diamonds and that the associated population of immediate family dependents could include 100,000 to 200,000 people. If those people that are indirectly dependent on artisanal diamond mining through forward and backward linkages are included, the World Bank estimate reaches 200,000 to 400,000 people dependent upon artisanal mining for the greater part of their livelihood. This represents between 4 percent and 8 percent of the population.

The Future

Notwithstanding its relatively small size, Sierra Leone is widely recognized as a highly prospective target for mining activities. The return to political stability in Sierra Leone coupled with positive global developments in the mining sector now offers the ideal opportunity to rejuvenate the domestic mining sector and to allow it to once again underpin the formal economy and support the Government’s developmental objectives.
Key developments that have significantly improved the prospects of the Sierra Leonean mining sector include:
  • The successful implementation of an IMF-supported economic reform programme, which has established a sound macroeconomic environment. Inflation has been kept under control, the exchange rate has stabilized, and access to foreign exchange has improved;
  • The introduction of the certificate of origin scheme and implementation of the subsequent Kimberley Process, which has facilitated a rapid return of diamond exports to official channels. This has drawn the attention of the international community, which has increasingly shown its willingness to support wider sector reforms; and
  • Strong global demand for minerals, underpinned by rapid growth in emerging economies such as China, which has fuelled an investment boom in the mining sector. Worldwide exploration budgets have quadrupled from US$1.9 billion in 2002 to an estimated US$7.5 billion in 2006, an increasing proportion of which is being spent in Africa. Of particular interest to Sierra Leone is the dominance of junior exploration companies in this revival, since they will be most likely to underpin the exploration investments needed to establish Sierra Leone’s mineral potential, and the increasing appetite of major mining companies to make large investments in high-risk, emerging economies.
While the resurgence of the Sierra Leonean mining sector has been impressive, it has so far focused on the re-establishment of closed mines or exploitation of previously proven reserves. There is now an urgent need to actively encourage new investment in the sector
Sector Assessments

The only attempt to quantify the economic potential of the Sierra Leonean minerals sector was a study undertaken jointly by the World Bank and the Government of Sierra Leone. Updated in 2005, the study concluded that successful realization of the country’s large-scale mineral potential could result in up to 8 mines within a decade, as follows:

Global production of diamonds reached 179 million carats in 2006, valued at over US$ 13 billion. Official diamond exports from Sierra Leone have begun to plateau. Total carats exported fell in 2005 and 2006, although the price realized per carat continues to rise. The only Kimberlite mine operator, Koidu Holdings, was forced to defer plans to mine a second pipe when the ore grade turned out to be sub-economic (although it is now understood to be investigating plans to mine a second pipe in late 2008 and proposes to develop its Tongo resources (kimberlite dyke deposit) as early as 2009.

Rutile and ilmenite

Rutile is a high-grade titanium ore, which is processed into titanium dioxide overseas for use mainly in paint, paper and welding rods. Sierra Leone is known for its particularly high-grade rutile. Titanium has a wide range of applications and is the metal of choice for the rapidly-growing aviation industry. In the medium-term, demand for the metal is expected to continue to be driven by the Chinese commodity boom.

Bauxite predominantly serves as a feedstock for aluminium production. The global market continues to grow with global production rising from 137 million tons in 2001 to 177 million tons in 2006. Sierra Leonean production makes up just under 1% of this volume. Vast reserves of bauxite are already proven, and as is the case for rutile, demand for bauxite in the medium-term will continue to be underpinned by robust economic growth in China and India


Globally, mineral exploration for gold has grown significantly in recent years, driven largely by the rapid acceleration in prices since 2004. The rapid emergence of a middle class in both China and India has led to significant increases in demand, while total gold output has remained largely unchanged since 2000. A recent characteristic of the gold market that could benefit Sierra Leone is the shifting pattern of global gold production away from the traditional producers. South Africa, Australia, the United States and Canada have all seen significant falls in production over the last decade, while new gold producing countries like Ghana and Tanzania have rapidly risen in prominence.

Exploration activity has resumed in recent years. Cluff Gold and Mano River Resources both have active appraisal programmes. The former continues to define the Baomahun discovery. Recent results have already identified a mineral resource of over 1.1 million ounces of gold, and a scoping study confirmed that an open-pit mine could produce between 140,000 to 200,000 ounces annually. Mano River Resources has three gold exploration concessions, which coincide with the richest traditional areas of artisanal gold working in Sierra Leone. All three deposits are considered to have the potential to host gold deposits significantly larger than the known gold deposits at Baohamun and Komahun.

  • Sierra Leone Ore and Metal Company mines at Mokanji at a rate of 1,5 million t per year.


Sierra Leone exported 603 623 ct of diamonds in 2007, in line with the previous year, but the value of sales rose to $142-million as quality improved, a government official said in January, 2008. The value of exports had increased from $127-million in 2006, when 603 868 ct were exported.


Sierra Leone is renowned for the quality of its diamonds and for the recovery of some of the most spectacularly large stones of very high value. The largest diamond, discovered in February 1972, was the 969,8 ct 'Star of Sierra Leone'. More recently, in 1996, two stones weighing 188 ct and 283 ct were recovered and sold. Annual output reached a peak of around 2 million ct in the late 1960's, with output declining thereafter. By 1997, output was seriously disrupted by RUF rebel activity, with most of the diamondiferous areas becoming off-limits.

Sierra Leone's established diamond fields cover an area of almost 20,000 km2 (over one- quarter of the country) in the southeastern and eastern parts of Sierra Leone. They are concentrated in Kono, Kenema and Bo Districts and are mainly situated in the drainage areas of the Sewa, Bafi, Woa, Mano and Moa Rivers. Kimberlites, the primary source of diamonds, were first discovered in 1948 in the Koidu area and subsequently at Tongo. Alluvial diamond concentrations occur in river-channel gravels, flood-plain gravels, terrace gravels and in gravel residues in soils and swamps. (Source: African Diamonds plc)

Diamond mining in the Yengema area, Kono District
Source: Sierra
  • Artisanal mining around the town of Koidu-Sefadu, in Kono District on the eastern border with Guinea and Liberia. Mechanized alluvial mining at the Magna Egoli alluvial mine along the Sewa River between the towns of Bo and Kenema. The mine was developed and run by Rex Mining of Antwerp until 2002, when operations were taken over by Fauvilla Ltd. and Waldman Diamond Resources of Israel.

Artisanal diamond mine in Sandoh chiefdom, Kono district, Sierra Leone. (Photo Courtesy Anna Jefferys/IRIN)

  • Energem Resources Inc (Canadian, ENM.TO) has a 40% stake in Koidu Holdings SA (Magna holds 35% and BSGR holds 25%) which is developing the Koidu kimberlite project as well as exploring three alluvial concessions Matemu, Upper and Middle Sewa and the Tongo Fields Kimberlite Dyke Deposit. Koidu comprises two pipes and four dyke zones and has estimated indicated and inferred resources of 1,52 million t @ 0,55 carats per tonne on the No. 1 pipe and 2,9 million t @ 0,26 carats per tonne (indicated and inferred resources) at the No. 2 pipe. Production for 2006 amounted to 80 152 carats with an average value of US$ 233 per carat (see video). By the end of 2007, the government of Sierra Leone had formerly ordered the temporary closure of the country’s sole operating kimberlite diamond mine after illegal mining activities by artisanal diggers in Koidu Holdings’ concession area made it impossible to safely exploit the deposit.
Koidu Kimberlite Project
  • Cream Minerals Ltd (Canadian, CRMXE.OB, CRMXF.OB, CMA.V) entered into an agreement with Casierra Diamond Corporation ("CDC") and its wholly-owned subsidiary, Casierra Development Fund Inc. ("CDF") (collectively, Casierra") to earn an interest in production from two exclusive prospecting licence areas for diamonds and other minerals and metals in Sierra Leone. Cream has the option to earn up to a 70% interest in the property. Casierra has been working in Sierra Leone since 1993 and obtained its first prospecting licence on the Sewa River, which drains the Kono diamond area. Kono is an important centre of diamond production in Sierra Leone with a high percentage of gem quality diamonds coming from kimberlite and alluvial sources. Extensive alluvial diamond exploitation has been carried out upstream of the CDF licence. In late 1994, CDF obtained its second offshore special Exclusive Prospecting Licence at the mouth of two rivers with extensive alluvial diamond mining activity, the Moa and the Mano. In a report written for the Geological Survey of Sierra Leone "The Diamond Fields of Sierra Leone", Hall (1966), reports production from 1950 to 1965 on the section of the river above the Sewa River licence, as 42,000 cubic yards with an average recovered grade of 0,75 carats per yard. He further reports 64,000 cubic yards production at similar grade for the same period from the section downstream from the licence and suggests substantial reserves remain in these areas. Based on study of the Sewa River placers and minor sampling, Hall presents an estimate for the section of the river contained within the licence area. He suggests 2,900,000 cubic yards at 0,4 carats per yard for the channel gravels and 1,500,000 cubic yards at 0,4 carats per yard for the flats and low terraces. Cream reported in August, 2007, that its joint venture partner, Casierra Development Fund Inc ("CDF") had applied for mining licences covering 31 acres (12 hectares) within its diamond exploration licence on the Sewa River in Sierra Leone. This will enable the joint venture to continue bulk sampling and start small scale mining of alluvial diamonds and gold. If, as anticipated, the licences are granted, the joint venture will be in a legal position to sell any production results after submitting the gem stones to the Government of Sierra Leone for royalty payment and the Kimberley Process Certification.
  • Mano River Resources Inc (Canadian, MNO.V) has created a new subsidiary Stellar Diamonds Limited to handle its diamond assets for which it plans to list on the Alternative Investment Market (AIM) in London within a year, the company announced on April 5, 2007. The company intends starting underground diamond production on the Kono kimberlite dyke joint venture with Petra Diamonds in 2008. Petra Diamonds has a 51% interest in the Kono Project. Diamond recovery from the first bulk samples from the Lion fissures commenced in June, 2006. Petra said in September, 2007, that test work had combined weathered, diluted and mixed underground diamondiferous kimberlitic material, which had yielded 2,809 diamonds, totalling 241.7 carats. The ten largest stones ranged from 7.2 carats down to 0.65. The work done then was too limited to determine a representative grade or value. Minerva Resources has a minority interest (24.5%) in the Lake Sonfon Diamond Project, operated by Manor River Resources. Mano River Resources has announced that reconnaissance work has confirmed the presence of macro-diamonds, one of which is classified as a clear white octahedral gemstone weighing 0.315 carats, and of kimberlite indicator minerals, within the Lake Sonfon JV area.
  • Stellar Diamonds Limited is the Sierra Leone subsidiary of Stellar Diamonds Limited , a company registered in the British Virgin Islands and is advancing the Tongo project in Sierra Leone to the mine development stage after a positive preliminary economic assessment demonstrated an NPV of US$53 million and IRR of 31% (pre-tax) through mining almost 1 million carats over an 18 year life of mine. The starting capital for the first four years is estimated to be US$24.8 million which will enable both surface and underground mining to be established. The proposed Tongo Mine (Tongo) is located in the Kenema District, Eastern Province of the Republican State of Sierra Leone approximately 45 km northnorth-east of the regional town of Kenema. The Tongo License is located on the ~3.0 Ga Leonean Province of the Archaean Man Craton (McFarlane et al 1981) that is comprised of typical granite-greenstone terranes of this age. The granitic areas comprise tonalite-trondhjemitegranodiorite-gneisses and these occupy approximately 65% of the Craton (Skinner et al 2004). Basic intrusives, mostly dolerites, of Triassic-Jurassic age cross cut the ancient basement. These dykes were emplaced during, and subsequent to, the continental rifting that separated West Africa from South America. Strong lineament development is also a hallmark of this event, and it has been suggested that these deep seated lineaments were used as pathways by kimberlite magmas during the Cretaceous (Haggerty, 1982; Venkatakrishnan & Cluver, 1989). The kimberlites in the Tongo diamond fields are mostly dykes of which four sets have been identified within the Tongo license and on both the neighbouring Koidu Holdings (Octea Mining) property and the former River Diamonds property (now held by Koidu Holdings) further to the south west. These have variously been named the Lando, Kundu, Peyima and Panguma dykes. In the Koidu Holdings license, dykes of at least three textural varieties of kimberlite have been recognised. The Tongo kimberlites have an estimated age of around 140Ma (see Skinner et al 2004) but no actual radiometric dating has been conducted on them. The Tongo dyke average thicknesses range from 30cm to 45cm, though in certain areas increased widths are noted. The strike is between 070 degrees and 088 degrees with vertical or near vertical dips.

  • African Diamonds plc (AFCDF.PK, also active in Botswana, Guinea) holds two exploration licences and a mining lease over a large tailing deposit. West African Diamonds plc (WAD) is a diamond focused explorer with operations in Sierra Leone and Guinea. Formed from the West African assets of AIM LIsted African Diamonds plc and recently acquire additional licences in Guinea. WAD contains a portfolio of development and advanced exploration assets across West Africa.
  • River Diamonds plc (RVD.L) is exploring the kimberlite dykes at Panguma adjacent to the Tongon diamondiferous kimberlite dykes. The company estimates that the kimberlite dykes on the concession represent between 1-million and 1,2-million tons of kimberlite. At an average grade of between 50 and 70 carats per hundred tons, this represents between 500 000 ct and 840 000 ct.
  • Sierra Leone Diamond Company Ltd and its wholly owned subsidiaries have assembled a portfolio of mineral rights in Sierra Leone, covering some 36,364 square kilometres, which rights include not only diamonds but in many cases also precious metals, base metals, iron ore, rutile, bauxite and rare earths. The focus is on the discovery of diamondiferous kimberlite deposits.

  • Target Resources plc operates through its subsidiary Milestone Trading Ltd and its Sierra Leone subsidiaries. Its main objective is the recovery of alluvial diamonds and gold in the Kono district of Sierra Leone.

Gold in Sierra Leone

Gold Home

Sierra Leone: Government Suspends Exploration Licences
January 17, 2007
Minister of Mineral Resources, Alhaji Mohamed Swaray-Deen told the Concord Times newspaper in an interview that government has decided to suspend further issuance of exploration and prospecting licences to potential and non performing companies.
Swaray-Deen explained that President Ahmed Tejan Kabbah recently reached an understanding with the government of the People's Republic of China to carry out exploration of all minerals in the country. "We will not issue out new licences for now. We will only renew exploration and prospecting licences to companies that have performed satisfactorily well.
Mining companies like Sierra Minerals and Koidu Holdings Ltd. will continue their work unhindered, Swaray-Deen said, adding that the Chinese were in the country and had already taken mineral samples for analysis.

"The next step will depend on the result of this analysis. Our aim is to create a data bank of all minerals in the country," he explained and reiterated that all companies that have performed satisfactorily well would be allowed to continue their work

The Archean Nimini Hills and Sula Mountains Greenstone Belts have banded iron formation and shear-zone-hosted gold occurrences.
  • Mano River Resources Inc. (MNO.V) holds seven gold properties in central Sierra Leone totaling approximately 750 km², which include Nimini, Sonfon, and Pampana North and South. Golden Star Resources Ltd (AMEX:GSS; TSX:GSC) has entered into a joint venture agreement (earning up to 85%) and is engaged in regional early stage exploration.
  • Cluff Gold plc ( CLUGF.PK, also active in Côte d’Ivoire, Burkina Faso and Mali) has a right to earn a 60 per cent interest in the Baomahun project in Sierra Leone to be acquired from Winston Mines which owns the two exploration licences relating to Baomahun covering an area of approximately 137 km2. A total of more than 9,000 m of drilling has been completed during 2005 and 2006 and a resource of more than 880,000 oz has been established to date.
  • West African Diamonds plc has commenced gold exploration in the Nimini Hills Greenstone Belt. Early reconnaissance sampling for gold at the Nimini Hills gave encouraging results.
  • Amara Mining plc's  Baomahun project ( see Cluff Gold above) has reached feasibility stage in Sierra Leone and is wholly owned by the Company. An updated resource estimate, consisting of 2.24Moz Au in indicated resources and 0.54Moz Au in inferred resources, is hosted in an area of approximately 2 sq. km, while the total project licence area is 136 sq. km. The Company has a two-fold strategy for Baomahun: to advance towards production with the current resources while delineating additional ounces along the 12km strike. The Company is advancing Baomahun towards its bankable feasibility study, which was due in H1 2013.  SRK Consulting Limited has completed an initial open pit mine schedule based on a US$1,150 per ounce gold price, which contained 1.2 million ounces of indicated resources at an average diluted grade of 2.23g/t and a strip ratio of 12.6:1. The indicative open pit also contains 0.1 million ounces of inferred resources which have been treated as waste in the initial analysis. This generates a  eight year mine life, producing 1.1 million ounces of gold at an average rate of 135,000 ounces per annum
Iron Ore

  • London-listed African Minerals has continued to build momentum since the attainment of its targeted 20-million-tonnes-a-year export run rate at Tonkolili in June 2013, posting quarterly iron-ore production of four-million tonnes – an 81% improvement on the prior three months. Mining capacity at the Sierra Leone-based operation continued to grow, with 5.5-million tonnes of material moved in the period, a 67% increase over the previous quarter. Exported grade improved slightly from 57.9% iron to 58.2% iron, while moisture levels remained stable at around 11%. Quarterly sales rose 65% to 3.4-million tonnes. As a result of the continued improvement in production, estimated cash costs fell from $49/t in the first quarter, to an average of $40/t in the second quarter. On the downside, African Minerals’ achieved free-on-board price in Sierra Leone declined from $89/t in the first quarter to $70/t in the second, attributable chiefly to a drop in the benchmark price, a higher proportion of sales into the Shandong agreement, adjustments on final invoicing and the additional discount associated with selling lump blend. The Tonkolili project boasts an estimated 60-year mine life and a Joint Ore Reserves Committee-compliant resource of 12.8-billion tonnes, and was being developed in a number of staged expansions. The next stage of project expansion would pursue the production of up to 35-million tonnes a year of 64% high-grade hematite concentrate, in conjunction with the expansion of the current port facilities at Pepel. African Minerals had also developed significant port and rail infrastructure to support the operation of the project, through its subsidiary African Rail and Port Services, in which the government of Sierra Leone has a 10% free-carried interest. Looking ahead, guidance for sales was reiterated at between 13-million tonnes and 15-million tonnes, in 2013, with production targeted at between 15-million tonnes and 18-million tonnes over the 12 months. African Minerals said in January,2014 it was aiming to increase its rate of production this year, with a second phase of expansion planned for the end of 2014. The company said it was targeting a sustainable production run rate of 20 million tonnes in 2014, which the company achieved at times last year.

  • London Mining plc started production at the Marampa mine in December 2011 and in 2013 produced 3.4Mwmt of sinter concentrate. The Company expanded production capacity to 5.4Mwmt/a in 2013, and is increasing it  further to 6.5Mwmt/a. Marampa has a mineral resource of over 1 billion tonnes of iron ore including a Probable Reserve of 539Mt grading 31.1% Fe, sufficient for over 40 years of mine life.
    London Mining slipped into administration in mid October 2014 after it ran out of funds and failed to secure a buyer for the company, but said that it would work with its administrator PricewaterhouseCoopers to ensure a buyer for the mine. 
    Iron ore miner African Minerals Ltd said in November 2014 it had agreed to provide Timis Corporation, owned by its Chairman Frank Timis, access for transporting ore from the Marampa mine, which the private company bought from failed miner London Mining. 
 Oil and Natural Gas

In October 2005, Sierra Leone signed an agreement with Nigerian’s oil and natural gas company, Frazimex Ltd, allowing the company to explore for oil in Block 3 for seven years. Several test wells drilled in the 1970's on Sierra Leone's continental shelf produced "shows" of oil.


  • Jubilee Platinum plc's York PGM Project. Joint venture (50%) with AIM listed Golden Prospect plc which covers the central section of the Freetown Layered Gabbro Complex, an area with a history of artisanal platinum production. A reconnaissance programme in early 2004 extended the known mineralization (soil samples assaying previously up to 0,84 g/t) of an anomalous 2 m-wide PGM zone to 8,5 km strike length from 5 km, with similar elevated PGMs in soil samples. A second-phase programme of trenching was completed in 2005.

Economic geology of nonmetal deposits

Economic geology of ore deposits

Economic geology, general

Economic geology, general, economics

Economic geology, geology of nonmetal deposits

Economic geology, geology of ore deposits