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Natural inclusions
Chemical process  






Most minerals contain visible traces of their genesis - perhaps tiny crystals of other minerals that were caught up in the growth of the larger host crystal, or formed simultaneously as it grew, internal fractures that have been partially healed during growth, or traces of earlier growth stages, marked by zoning. Gemologists use the word inclusions to describe these and other internal phenomena.

Inclusions in a gemstone, viewed through a microscope or a 10x loupe, can give information about the geological environment in which the mineral was formed.

Inclusions can sometimes identify gemstones and they can prove whether the stone is natural or synthetic. Inclusions can also tell us where a gemstone comes from

Diamond with Garnet
 Solid inclusions may be the same gem type as the host, or different like the garnet in this diamond.

Inclusions can  indicate about the geologic origin of the stone. They can tell you the story of the gemstone formation: They are the natural trademark of the stone! The proof of its natural, synthetic or treated status.

Insect in Amber

Inclusions are extremely precious to the gemologist as more synthetics and treated stones are present in the market everyday. Learning to recognize these inclusions is essential knowledge for the gemstone buyer as he will be better able to separate the fine natural gems from material that is the result of human expertise in crystal growing or heat treatment.
Gemologists classify inclusions in 3 groups:
Protogenetic: Which were formed before the gemstone host, they are always mineralistic, typically crystals more or less corroded.
Singenetic: That formed at the same time as the host crystal. They were imprisoned inside it during its formation or have appeared during its cooling as rutile needles in rubies and Epigenetic: Formed after the gem was grown. Typical from this type are limonite, iron staining or oil that can fill the natural fissures of the gemstones.

Rectangular cavities with tails are sometimes found in Indian Emeralds.

Almandine Garnet
The bright interference colours at the bottom are due to zircon crystals

Needle like rutile inclusions are sometimes found in Quartz

The insect like inclusions are a common feature of  Moonstone

Furthermore, some inclusions are just beautiful in themselves: Golden needles in high luster quartz, insects trapped in Amber, fine liquids of incredible complexity in sapphire, crystals looking like star ships in rubies, cavities with tails in emeralds, or sapphires. Some gemstones rely on their inclusions for their effect, like aventurine quartz, or star sapphires. Green aventurine quartz is actually colourless quartzite, filled with tiny flakes of green fuchsite mica that lend it colour.

Rutile Needles in
Rock Crystal

Star sapphires are filled with elongated crystals of rutile (often called 'silk') arranged in three directions parallel to the faces of the hexagonal prism. When such a stone is cut in a dome shape, with its base parallel to the basal plane of the crystal, a six-pointed star (or sometimes a twelve-pointed one) is seen in the reflected light of the sun or a spotlight.


Star Sapphire

Inclusions are definitively no longer considered blemishes that lower the value of gemstones. They are precious and beautiful wonders that unquestionably add value to them! The recognition and the understanding of these inclusions is a key skill to learn for all gemologists or gemstone buyers who want to know which stones they are dealing with

Inclusions that look like water lily leaves are a typical feature of peridot.

Natural Gemstones




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