Hydrothermal deposits are mineral deposits formed from solutions containing volatile and metallic elements heated by late stage magmatic activities. Changes in external environment result in the decrease of temperature and pressure, inducing the precipitation of these elements from the solution, which then formed mineral deposits. An example of gemstones from hydrothermal deposits is emeralds from Columbia ; other minerals include crystals, agates, chalcedony, fluorites, opals and rhodochrosites.