Argillaceous limestone, Lancashire. Britain

Fine-grained argillaceous Carboniferous Limestone shows widespread replacement of fossils by pyrite and marcasite.

Major Minerals:

Pyrite, marcasite

Minor Minerals:

Carbonaceous matter, TiO2 minerals

Trace Minerals:

Includes detrital zircon


The carbonaceous matter shows variations in reflectance. Fine-grained intergrowths of pyrite and marcasite have replaced carbonates within fossil clasts but preserved many organic textures. Framboidal pyrite has recrystallized to euhedral crystals.