Inklusions

Inclusions are materials that are trapped within another mineral or rock during its formation. They can be solid particles, liquid pockets, or gas bubbles enclosed by the host phase. In geology and materials science, inclusions preserve samples of the environment and conditions present at the time of crystallization or metamorphism, making them valuable records of geological history.

Common types of inclusions include solid mineral inclusions, which are fragments of other minerals encased in a growing crystal; fluid inclusions, which are microscopic droplets of liquid (often aqueous brines) or immiscible fluids trapped within mineral lattices; and gas inclusions, which consist of bubbles of vapor such as CO2 or hydrocarbons. In diamonds, for example, mineral and fluid inclusions can reveal mantle composition and the pressure–temperature conditions of deep Earth.

Inclusions form when a crystal incorporates foreign material during growth or when rocks are subjected to later changes that trap fragments or fluids in pre-existing crystals. They may also develop along fractures or as a result of exsolution and deformation processes. The study of inclusions often requires specialized techniques because the inclusions are typically microscopic and may be altered by subsequent geological processes.

Analytical methods used to investigate inclusions include polarized light microscopy, Raman spectroscopy, and microthermometry of fluid inclusions to determine temperatures of entrapment. More advanced approaches—such as electron microscopy, X-ray computed tomography, and isotopic or elemental analyses—provide detailed compositions and ages. Inclusions thus contribute to fields ranging from mineralogy and petrology to economic geology and planetary science.