INCLUSIONS are internal features of gems. They may be solids, liquids, or gases that the crystal enclosed as it grew, or cleavages, cracks, and fractures that filled (or partly filled) after the host material finished growing. Although usually regarded as flaws, inclusions today are often seen as adding interest to a stone. They can also be invaluable in identifying a gem, because some are peculiar to a particular species, while others occur only in a particular locality.
MICROSCOPE
FORMATION OF INCLUSION
Solid inclusions have usually formed before the host stone - the crystals of the host have grown around them and enclosed them. They may be distinct crystals or amorphous masses. Solids and liquid inclusions formed at the same time as the host are aligned to its atomic structure. For instance, the stars in star rubies and sapphires are caused by needle-like crystals of rutile, which formed parallel to the crystal faces at the same time as the host corundum crystals. Cavities filled or fractures healed after the formation of the host give inclusions that resemble feathers, insect wings, or fingerprints.
DIAMOND WITH GARNET
Solid inclusions may be the same gem type as the host,or different like the garnet in the diamond.
PERIDOT "WATER LILY"
Inclusions that look like water lily leaves are a typical feature of peridot from Arizona, USA. They consist of a central chromite crystal surrounded by liquid droplets.
MOONSTONE "CENTIPEDES"
These insect-like inclusions are a common feature of moonstone. In fact they are parallel cracks caused by strain.
RUTILE NEEDLES
This carved rock crystal perfume bottle contains inclusions of needle-like rutile crystals. Tourmaline and gold are also found in rock crystal.
INSECT IN AMBER
Insects are sometimes found trapped in amber, caught by the sticky resin as it was exuded. Insects have been added to some imitation amber to create a natural effect..
ALMANDINE GARNET
Magnified 45 times, the grey patch on the left is a rounded apatite inclusion. The bright interference colours to the right are due to a zircon crystal.
EMERALD (LEFT)
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