Magnetite and haematite. Skye, Scotland.
Magnetite (pink-brown, right) is coarse-grained and is intergrown with haematite (white, centre), which encloses an euhedral basal section of quartz (dark grey, centre bottom). Silicates are dark grey (left), black areas are polishing pits.Coarse-grained magnetite is often difficult to polish well.
Polished block, plane polarized light, x 40, air