Galena, sphalerite and pyrite. Shullsburg, Wisconsin, USA
Pyrite (yellow-white, centre) as lath-shaped crystals has been extensively replaced by galena (blue-white, centre) and minor sphalerite (light grey, centre right). This replacement is crystallographically controlled. Inclusion-free galena (centre right, bottom centre) is intergrown with replaced pyrite and with sphalerite. Sphalerite (light grey, bottom right and left) is inclusion-free. Dark grey areas are carbonate (top) grains.
Polished block, plane polarized light, x 80, air