Rammelsbergite. Great Bear Lake, Canada
A typical dendritic habit of rammelsbergite (white) in this association. The cores of the dendrites are carbonates, especially dolomite (grey, centre, centre left). Calcite, the main gangue, shows bireflectance between adjacent crystals (centre top). The colour and reflectance of rammelsbergite in this photomicrograph are not affected by the presence of native silver and so the mineral appears white.
Polished block, plane polarized light, x 80, air