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Iridescent Chalcopyrite crystal cluster (Peacock Ore) / Reynolds County, Missouri
Botryoidal minerals form when many nearby nuclei, specks of sand, dust, or other particles, are present. Layers of mineral material are deposited radially around the nuclei. As more material is deposited, the spheres grow larger and eventually overlap with those that are nearby. These nearby spheres are then fused together to form the botryoidal cluster.