Columbite, cassiterite, ilmenite and zircon. Jos Plateau, Nigeria

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A river placer that comprises a mixture of oxides and silicates. Cassiterite (light grey, centre) has small columbite (light brown, higher reflectance, centre) inclusions. Ilmenite (pink-brown, bottom left) has altered along its edges to porous haematite (grey), but the unaltered ilmenite core has higher reflectance and a stronger surface colour than columbite (brown-grey, top right, top left). Zircon (grey, bottom left) has fine-grained haematite inclusions (higher reflectance) which are responsible for the incipient red internal reflections.

Grain mount, plane polarized light, x 180, oil

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