An inclusion ( lat . Inclusio "inclusion") is a foreign matter (liquid, gas, petroleum , natural asphalt or another mineral) enclosed in a mineral .
In mineralogy, a distinction is made between primary inclusions, which emerged in the interstices in the hydrothermal stage before the crystal formation was complete, and secondary inclusions, which only emerged after crystallization.
The most well-known inclusions are mineral needles (e.g. rutile needles ). These inclusions arise when the existing mineral needles are enclosed by another mineral (e.g. quartz ), the second crystal then grows around the first. Quartz in particular often contains small or large inclusions, such as asphalt (stinky quartz), hematite or the rutile needles mentioned above.
Inclusions can also grow simultaneously with the surrounding crystal. If the mother crystal temporarily stops growing, other minerals can settle on it. When this continues to grow, it encloses the newly formed crystals, which remain as inclusions in the mother crystal.
Inclusions of gases or liquids ( fluid inclusions ), if they were included during crystal growth, are among the primary inclusions. If they get into the crystal through cracks and fractures only after the growth has been completed (partly also through the decomposition of enclosed minerals), one speaks of secondary inclusions.
Often the gas or liquid bubbles with a diameter of less than 0.1 mm are not particularly large. Inclusions can be used to draw conclusions about the formation of the crystals, e.g. B. on the formation temperatures and conditions.
If small inclusions are present in large quantities, this can lead to light phenomena. Examples are tiger's eye or labradorite . Here the quartz replaces another mineral ( pseudomorphism ), but does not grow in its normal crystal form, but in the form of the former mineral that has already grown.
- Jaroslav Hyrsl, Gerhard Niedermayr: Inclusions in quartz. Inclusions in quartz. , ISBN 3-925094-81-4
- Eduard Josef Gübelin , J. Koivula: Picture atlas of the inclusions in precious stones , 1986. ISBN 3-85504-094-X
- R. Rykart: Bergkristall , 1977. ISBN 3-7225-6249-X