Quartz veins. Ririwai, Nigeria

Centimetre to decimetre-wide quartz-cassiterite-sphalerite veins have greisenized borders, and cut biotite granite.

Major Minerals:

Sphalerite, cassiterite, galena, chalcopyrite, wolframite

Minor Minerals:

Molybdenite, pyrite, marcasite, arsenopyrite, stannite group minerals, pyrrhotite

Trace Minerals:

Include bismuthinite, native bismuth, cubanite, mackinawite, lead and copper sulphosalts, aikinite, native gold


Cassiterite is optically zoned and twinned and carries small columbite and TiO2 mineral inclusions. Sphalerite forms a number of generations and carries crystallographically oriented stannite and coarse-grained chalcopyrite-pyrrhotite-cubanite-mackinawite inclusions formed by the unmixing of iss. Sphalerite has suffered extensive chalcopyrite disease along fractures and grain boundaries, very fine-grained chalcopyrite-disease has changed the surface colour of sphalerite. Chalcopyrite has exsolved sphalerite stars and rounded pyrrhotite-cubanite-mackinawite inclusions. Stannite forms rims between sphalerite and chalcopyrite. Galena encloses numerous fine-grained inclusions of bismuth, bismuthinite, stannite and silver-bearing phases


Kinnaird et al., 1985; Kinnaird, 1985; Pastor and Turaki, 1985; Ixer et al., 1987