Inclusion (mineral)

File:Inclusion.JPG

Quartz crystal with chlorite inclusion.

In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation.

In gemology, an inclusion is a characteristic enclosed within a gemstone, or reaching its surface from the interior.

According to Hutton's law of inclusions, fragments included in a host rock are older than the host rock itself.

Mineralogy

Inclusions are usually other minerals or rocks, but may also be water, gas or petroleum. Liquid or vapor inclusions are known as fluid inclusions. In the case of amber it is possible to find insects and plants as inclusions.

The analysis of atmospheric gas bubbles as inclusions in ice cores is an important tool in the study of climate change.

Contrast with xenolith.

Gemology

Inclusions are one of the most important factors when it comes to gem valuation. In many gemstones, such as diamonds, inclusions affect the clarity of the stone, diminishing the stone's value. In some stones, however, such as star sapphires, the inclusion actually increases the value of the stone.

Many colored gemstones, such as amethyst, emerald, and sapphire, are expected to have inclusions, and the inclusions do not greatly affect the stone's value. Colored gemstones are categorized into three types as follows:

• Type I colored stones include stones with very little or no inclusions. They include aquamarine, topaz and zircon.
• Type II colored stones include stones that often have a few inclusions. They include sapphire, ruby, garnet and spinel.
• Type III colored stones include stones that almost always have inclusions. Stones in this category include emerald and tourmaline.

• Gem with inclusion.JPG

  Clear gemstone with metallic inclusion.

• Peridotgem.JPG

  Peridot with milky inclusion.

• Ruby gem.JPG

  Natural Ruby with inclusions.

References

• Canadian Institute of Gemmology
• International Gem Society

de:Inklusion (Mineralogie)