Location:

Cligga Head, Cornwall, Britain

Within the Cligga Head granite, multi-stage tin-tungsten base metal sulphide mineralization occurs within thin quartz veins that have narrow greisen borders. The veins form a sheeted network cutting the granite. The earliest assemblage is cassiterite, wolframite and stannite, followed by arsenopyrite, pyrite, chalcopyrite, sphalerite and minor amounts of bismuth and molybdenum minerals, followed by pyrite, chalcopyrite and minor cassiterite and finally haematite and limonite.

Major Minerals:

Cassiterite, arsenopyrite, wolframite, chalcopyrite, pyrite

Minor Minerals:

Sphalerite, stannite group minerals, haematite

Trace Minerals:

Include molybdenite, native bismuth, chalcocite

Textures:

Tabular wolframite is optically and compositionally zoned and is intergrown with zoned and twinned equant crystals of cassiterite. Euhedral arsenopyrite is twinned and is intergrown with chalcopyrite, sphalerite and stannite group minerals. Supergene replacement of the primary sulphides and arsenides is widespread

References:

Jackson et al., 1977; Moore and Jackson, 1977; Charoy, 1979