‘Coltan’ is the abbreviated name for ‘columbite–tantalite’, a group of dense, black metallic ores that contain both niobium minerals (columbite) and tantalum minerals (tantalite) in varying proportions. Columbite is named after niobium’s historical name, columbium.
Industry participants often just call this mineral ‘tantalite’ because the value of the contained tantalite is several times that of the contained columbite. A description of how to calculate the value of columbite–tantalite is available here.
Columbite–tantalite is mined in many countries around the world and further information about its production is available here.