Microclinized granite. Ririwai, Nigeria

Major Minerals:

Cassiterite and wolframite

Minor Minerals:

Zircon, monazite, thorite, TiO2 minerals, haematite, molybdenite, sphalerite, coffinite


Fine-grained (< 1µm) haematite crystals characteristically are aligned along the cleavage planes of microcline (to give reddened feldspar in hand specimen). Biotites alter to Li-Al-rich micas and have TiO2 minerals and haematite lying along their cleavage planes. Accessory and opaque minerals are associated with phyllosilicates as fine-grained aggregates


Ixer et al., 1987; Pointer et al., 1988a,b