The rock formations in caves are chemistry fossils — that glow. These rocks are made of calcite, a form of calcium carbonate. Impurities trapped in calcite cause the mineral to fluoresce different ...

Usually the original mineral was aragonite or calcite, and it has been replaced by silica (in ... well-cemented sediment in the middle of a relatively uncemented sedimentary rock). Indeed, the critter ...

Discover the history and properties of lapis lazuli, a stunning blue rock prized for its color and gemstone uses.