The mineral pyrite is an iron sulfide (FeS2) commonly found in organic rich sedimentary rocks. There is nothing more mesmerizing to a microscopist when analyzing a shale sample then coming across a multitude of pyrite framboids (a texture described from the French word “framboise,” for raspberry). Framboidal pyrite stand out like a bright sun against the backdrop of darker and much duller clays and organics.
So, while most “Beauty in Geology” content is about beautiful landscapes and formations, the micro can be just as beautiful as the macro to geologists.
We hope you enjoy these images of pyrite framboids in Marcellus Shale taken with a Field Emission Scanning Electron Microscope.
If you are interested in learning more about pyrite framboid formation we highly recommend Wilkin and Barnes, 1997, Formation Processes of Framboidal Pyrite, Geochimica et Cosmochimica Acta, Vol. 61, No. 2 pp 323-339.