Agatized coral occurs when silica in the ocean water hardens, replacing the limy corals with a form of quartz known as chalcedony. This long process (20-30 million years) results in the formation of a "pseudomorph," meaning that one mineral has replaced another without having lost its original form. (excerpt Dept of FL State)
Agatized corals are used for shamanic work, connecting and working with ancestors as well as lower chakra work.
These are beautiful polished tumbled stones, each with a unique patterning. Sizes do vary from around an inch.