Inclusions

An inclusion is material that is enclosed within another material and is not part of its primary matrix. Inclusions can be solid particles, liquid droplets, or pockets of gas, and they may form during formation, processing, metamorphism, or biological activity. The term is used across disciplines, with context shaping its meaning.

In materials science and engineering, inclusions are typically foreign phases such as oxides, sulfides, silicates, or carbides embedded in a metal or ceramic matrix. They can originate from imperfect purification, impurities in raw materials, or segregation during solidification. Inclusions influence properties in various ways: they can degrade mechanical performance by acting as sites for crack initiation or corrosion, but certain microstructural inclusions or precipitates can also enhance strength or wear resistance. The impact depends on size, shape, distribution, and the interaction with the surrounding matrix. Detection and characterization generally involve optical and electron microscopy, often with elemental analysis to identify composition.

In geology, inclusions are materials trapped within a growing mineral. They provide records of the environment and conditions at the time of formation. Fluid inclusions contain minute quantities of melt or aqueous fluid and are studied to infer pressure–temperature history, salinity, and fluid evolution of rocks and minerals.

In biology and medicine, cellular and tissue inclusions refer to material such as lipids, pigments, or viral or protein aggregates that reside within cells. Some inclusions are normal cellular components; others can indicate disease processes or infections.

Overall, inclusions affect material behavior and interpretation of geological or biological histories, making their study important across several scientific fields.