Pyrite, jamesonite, sphalerite and galena. Ireland
180µm
Pyrite (pale yellow) is rhythmically banded with the growth bands picked out by very fine gangue inclusions. Pyrite has nucleated on sphalerite (light grey, top right) and on galena (blue-white, bottom left). Pyrite has been fractured and recemented by calcite (dark grey, bottom left), which shows multiple twinning (top centre) and faint light internal reflections. A blue-white acicular to tabular sulphosalt (centre) has a similar reflectance to galena, but is better polished and is highly anisotropic; it has the optical properties of jamesonite.
Polished block, plane polarized light, x 110, air
