Tungsten and bismuth minerals, including russellite, within greisen veins in the western Mourne Mountains, Northern Ireland

Primary and secondary W-Bi minerals are minor components of two greisen veins associated with the Palaeocene Mournes Granite Complex in Northern Ireland. The primary mineral, ferberite (wolframite with Fe>Mn), forms 2-3mm crystals associated with well-crystallized quartz in a vein through greisened granite. Associated with the ferberite crystals is a suite of secondary Fe-W-Bi-Mo minerals that formed during late-stage hydrothermal or supergene alteration. These comprise bismutite, russellite, a Bi-bearing, hydrated Fe-W mineral similar to hydrokenoelsmoreite (formerly ferritungstite), and an intergrowth of scheelite with an unknown Ca- and Mo-bearing mineral. This is the first record of these secondary minerals (apart from scheelite) from Ireland. Microprobe analyses and back-scattered electron images reveal a range of mineral compositions and replacement textures that help to explain the mineral forming processes. The occurrences are comparable to W-Bi-Mo mineralisation in SW England and the English Lake District.