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Fossil Shell on Calcite

Everything in geology connects, directly or indirectly. Magmatism and sedimentation may seem unrelated, but when they occur in the same region at different times, unusual combinations can emerge. I’ve always loved specimens where fossils meet Minerals, they spark questions of how.

This piece pairs a fossilized shell with azurite from Kerrouchene, Morocco. I’m not well-versed in the local stratigraphy, but even with limited knowledge, the specimen speaks. Agates are known from Triassic basalts in Kerrouchene. Basalts are richer in sulfur than felsic rocks, so they can host more copper. Primary copper minerals like chalcopyrite may crystallize as accessories. Later, circulating fluids oxidized these to secondary copper Minerals like malachite and azurite. Unlike agates, which require higher temperatures, these formed at low temperatures, plausibly in association with fossil deposition. No reference herein, just share some thinking process.

Busy Denver days, but glad to jot this down.

Shell on azurite, 3.5 cm, Kerrouchene, Kerrouchen Caïdat, El Kbab Cercle, Khénifra Province, Béni Mellal-Khénifra Region, Morocco

Jingnan (Tom) Zhang Coll, @finemineralphotography Photo