Location:

Lead-silver ore. Sark's Hope Mine, Sark, Channel Islands

Lead-silver veins cut and brecciate a Late Precambrian granite and lie beneath a silver-rich gossan that was mined out in the nineteenth century. Haematite, quartz, calcite and illite are the main gangue phases.

Major Minerals:

Galena, pyrite

Minor Minerals:

Chalcopyrite, tetrahedrite-tennantite, sphalerite, marcasite

Trace Minerals:

Include bornite, enargite group minerals, pyrrhotite, arsenopyrite, pyrargyrite, pearceite, acanthite, polybasite, covelline, blaubleibender covelline

Textures:

Pyrite, haematitic quartz and galena are rhythmically banded. Chalcopyrite is intergrown with tetrahedrite and pyrargyrite. Bravoite and tetrahedrite-tennantite show compositional zoning as reflectance and surface colour variations. Tetrahedrite is associated with chalcopyrite, whereas tennantite is intergrown with galena. Galena carries fine-grained tennantite, pearceite, polybasite, acanthite and pyrargyrite inclusions; many of these lie along growth zones in galena. Light etching of the silver sulphosalts is rapid. The presence of fine grained argentian minerals (less than 10 (m) in galena is common in 'argentiferous galena'.

Reference:

Ixer and Stanley, 1983