3" Colorful Polished Fossil Coral Sphere - Indonesia

About Fossil Coral From Indonesia

These fossil corals are approximately 20 million years old, dating to the Miocene epoch, and represent the preserved remains of vibrant ancient reef systems that once flourished in warm, shallow seas teeming with marine life. Indonesia sits at the heart of the Pacific “Ring of Fire,” where intense plate tectonics have uplifted massive sections of former seabed—coral reefs included—thrusting them skyward as volcanic mountain ranges formed. Over millions of years, these corals were buried by sediment and slowly fossilized in mineral-rich groundwater environments.

During this process, the original organic skeleton was replaced and infilled by a complex blend of silica, iron, manganese, calcium, and trace elements, often producing exquisite agatized preservation with rich banding, druzy crystal pockets, and occasional metallic dendrites formed by manganese or iron oxides. Unlike many fossils that compress or distort, coral fossils frequently preserve their original 3D colony structures—including delicate corallite cups, growth branches, and surface textures—making them an unusually faithful archive of reef morphology. Some specimens also record micro-borings left by sponges, worms, and bivalves, frozen mid-process before mineralization sealed them