Fluid inclusion

A fluid inclusion is a cavity, often ultra-microscopic in size, within a mineral in which one or more fluid, liquid and/or gaseous phases, sometimes accompanied by one or more solids, are trapped. There are primary fluid inclusions and pseudo-secondary fluid inclusions which formed before crystal growth had finished, and secondary fluid inclusions which formed by the healing of later fractures. The study of fluid inclusions gives information about the physical-chemical conditions that existed when the mineral was deposited and the geological events that occurred afterwards.