A combination of ethnicity and nationalism can cause ethnic "separation" since some ethnicities may feel the need to form a nation of their own, although this is not always the case.
Explanation:
On February 5, 1885, Belgian King Leopold II established the Congo Free State by brutally seizing the African landmass as his personal possession. ... The people of the Congo were forced to labor for valued resources, including rubber and ivory, to personally enrich Leopold.
This is geography and the answer is coal oil and gold as well as iron, and nickel