Mali’s many minerals

Deborah Painter (USA)

Mali is frequently associated with the Tuareg rebel insurgents, poverty and the desertification we see in the 2023 news items about the country. I also think of Mali in terms of the healthy recipes using fish, green pepper, sorghum, spinach, rice, peanut butter, and other ingredients in a cookbook of Mali traditional foods a friend gave me. There are, then, many aspects to various conflict-plagued African countries, not evident from the snippets of information we receive.

At an October 2023 gem show in the USA, I met a dealer named Kamar Kisman, who told me he had a friend in Mali who is an artisanal miner in the north-central Tombouctou Region along the Niger River and south of where the famed city of Timbuktu (Tombouctou), still stands.

My mind naturally wandered when he spoke of a place now synonymous with remoteness and romance. However, it was actually an important crossroads for many traders of West Africa beginning in the 1300s and continuing until the 1700s. The wealthy ruler of the kingdom of Mali, Mansa Musa, established three mosques in Tombouctou for Islamic studies, mathematics and history. At its peak, Tombouctou’s University of Sankoré enrolled approximately 25,000 students.

My reverie about the fabled city ended and I mentally returned to the mineral specimens spread before me. They had no labels and were separated according to the mineral groups. I needed identification for several. Mr. Kisman told me that the minerals were mined, trucked to an airport, and then exported by air to the United States. That seemed to me to be a very expensive process not reflected in the reasonable prices for these minerals he was selling. The minerals he had on display included epidote (Fig. 1), Prehnite, Green Garnet and Black Garnet. Elsewhere at the show, another dealer sold Malian Dogtooth Calcite.

Epidotes belong to a group of colourless, yellow-green or green silicate minerals. This group is composed of calcium, manganese, cerium, ferric iron or aluminium. Epidote features either thin prismatic or thicker tabular crystals (Fig. 2). Epidote is found in igneous and metamorphic rocks. The hardness of this mineral is 6.0 to 7.0 on the Mohs scale and is suitable for jewellery.

Prehnite is one of the oddest looking minerals you will see. It occurs in masses resembling sea green coloured bubbles or perhaps round green grapes growing singly or in clusters (Figs. 3 and 4). It is composed of calcium, aluminium and silica, has a hardness of 6.0 to 6.5 on the Mohs scale, and has a greasy lustre.

The mineral is most often found as a vein in basaltic volcanic rock that has been subjected to metamorphism caused by shallow burial of the basalt, or by hydrothermal activity. Sometimes, it occurs in hydrothermal veins in rocks other than basalt. A broken piece of Prehnite reveals a crystalline structure within (Fig. 5). Prehnite can be tumbled for use in jewellery.

Garnet is a name for a group of common silicate minerals, which are often found in garnet mica schist rock. Garnet is composed of silicon, with either magnesium, chromium, calcium, iron or aluminium, or varying combinations of these five. Mali Garnet can be clear, red, green (Fig. 6) or black (Fig.7). Mali’s unique garnet is found in alluvial deposits. It is actually a blend of the glossular and andradite species of garnet. The hardness of 6.5 to 7.5 on the Mohs scale also makes it a good stone for jewellery.

Dogtooth Calcite (Fig. 8) is a variety of calcite that forms as multiple crystals with faces that are all unequal, hence the name “dogtooth”. Colours range from white to grey, golden brown, tan or purple. Dogtooth Calcite is found in any open space that contains undisturbed standing calcium-rich water for an extended period. Such spaces can be caves, geodes and fractures in limestone. Calcite is composed of the elements carbon, calcium and oxygen. Dogtooth Calcite can be pure or can have inclusions of barite or galena. Its hardness on the Mohs scale is 3.0, and is a soft mineral best left unaltered.

Mali is located within two main geological structures, the West African craton in the western portion and the Tuareg shield in the southeast. The West African craton is a relatively flat topography with sandstone and alluvial quartz underlain by granite and shale. The Tombouctou Region of the West African craton consists of Quaternary alluvium and exposures of Paleogene and Neoproterozoic granites and volcanic rocks (Fig. 9). The Kayes Region in the southwest corner, a major source for gold and most other exported minerals, is similar geologically to the Tombouctou area near the Niger.

Mali’s gold and diamonds constitute a crucial portion of its economy. The gold is mined by large scale international mining conglomerates. The diamonds are still mined by artisanal miners, as are the minerals I saw at the gem show.

The artisanal miners (Fig. 10) work in small mines, often working in literal narrow holes in the ground, or in short narrow tunnels running parallel to the ground surface. These feature thatched roof openings for easy ingress and egress. Women constitute a large percentage of mine workers. Safety is not emphasised by the companies that employ the miners. In fact, the companies often do not provide personal protective equipment and workers must train others and manage their own safety using good judgment. Miners often have to clear trees to dig new pits and mines, all with minimal training in the use of tree clearing equipment.

In a 2021 interview for Michel Yao and Sory Kondo’s YouTube video on Mali mining (see References, Artisanal gold mining in Mali is an economic boon and an environmental disaster – YouTube), Modibo Mao Makalou, President and General Director of IBS Mali and advisor to the former Mali President Keita, stated that mining companies will spend a small amount on drinking water and roads for the greater community, but it is not enough. A national sovereign wealth fund is needed for the gold and other mining revenues, and a system needs to be in place for the state to make the necessary investments. International corporations, said Mr. Makalou, cannot be expected to come in and develop the country.

Dedicated to the memory of Paul S Knight.

About the author

Deborah Painter is an ecologist and general environmental scientist. She lives in the United States.

References

Campbell, Bonnie K., Editor. 2013. Modes of Governance and Revenue Flows in African Mining. United Kingdom: Palgrave Macmillan. 253 pages.

Hilson, G. M., Editor. 2003. The Socio-Economic Impacts of Artisanal and Small-Scale Mining in Developing Countries. Netherlands: CRC Press. 766 pages.

Pellant, Chris, and Helen Pellant. 2020. Rocks and Minerals. United States: Princeton University Press. 208 pages.

Yao, Michel, and Sory Kondo. 2021. Artisan gold mining in Mali is an economic boon and an environmental disaster.

Artisanal gold mining in Mali is an economic boon and an environmental disaster – YouTube