Africa is a continent that is very rich in mineral resources. However, even with these riches, it is a very poor continent, relatively speaking.
Much of Africa is not very economically useful. This is particularly true of the desert areas in northern Africa (the Sahara) and in southern Africa (the Namib and the Kalahari). Much of the rest of Africa is populated by people who are subsistence farmers. This means that they do not really produce much that goes into a larger economy. They just grow and raise the things on which they subsist.
The mineral wealth of Africa is not evenly distributed. For example, there is oil in the countries of Northern Africa and in Nigeria, but not in many other places. There are massive diamond mines in South Africa and smaller deposits in other countries such as the Democratic Republic of Congo. There are many other minerals to be found in Africa. These include gold, copper, chromium, manganese, uranium, and cobalt.
While Africa does have all this mineral wealth, it is not a very rich continent. This is partly due to a lack of development of infrastructure such as roads and electric grids. It is also because of the legacy of the time when Africa was colonized by the European powers.