21.5" Calcite & Aragonite Stalactite Formation
This enormous formation of calcite coating aragonite comes from Ighoud, Morocco. This large mass of mineral was removed from a cave where stalactite formations from iron-rich matrix are enshrouded in layers of aragonite and calcite crystal. About a third of this specimen has a web-like structure, while the rest is covered in a mass of aragonite crystal cluster.
Stalactites form when water that seeps through rock, reaches an opening such as a cave or tunnel. Once this mineral rich water (calcite in this case) precipitates out of the rock wall/ceiling, it leaves behind a crystal as the precipitate builds with each drop of water. Stalagmites are likely to form from this process, for the drops from the ceiling will still contain high mineral content, typically depositing a precipitate that will continue to build as long as water continues to flow in this location.