Thai Sapphire Inclusions

First Published: 7 September 2026

Thai Sapphire Inclusions

Explore Thai sapphire inclusions in Hyperion, the Lotus Gemology inclusion database. Hyperion contains photomicrographs of inclusions and internal features in natural sapphires from Thailand, documented with information on treatment, lighting conditions, field of view, photographer and published references.

In yellow and orange sapphires from Chanthaburi, Thailand, a thin layer of iron-rich silk is often found just under the table.
Angular dislocation needles interesect in this sapphire from Thailand.
Basal parting seen on the back of a black star sapphire from Chanthaburi, Thailand. Note the step-like appearance. Basal parting in these stones is due to exsolution of hematite/ilmenite silk, which produces both the star effect and a lack adhesion.
A small rhombohedral parting plane on the girdle of a black star sapphire from Chanthaburi, Thailand. This parting is cause by exsolution of boehmite, which produces a lack of adhesion.
Basal parting seen on the back of a black star sapphire from Chanthaburi, Thailand. Note the step-like appearance. The two diagonal lines are rhombohedral parting planes. Basal parting in these stones is due to exsolution of hematite/ilmenite silk, which produces both the star effect and a lack adhesion.
This black star sapphire had large pits on the base filled with dopping varnish. Following removal of the varnish by soaking in alcohol, the 75-ct stone lost about 0.25 ct of weight. But careful examination after the varnish removal revealed something far more sinister, a layer of glass coating the inside of the cavities. In addition, we could see the the glass extended across much of the base, as clearly revealed after immersing the gem in di-iodomethane.
This black star sapphire had large pits on the base filled with dopping varnish. Following removal of the varnish by soaking in alcohol, the 75-ct stone lost about 0.25 ct of weight. But careful examination after the varnish removal revealed something far more sinister, a layer of glass coating the inside of the cavities. Note the perfectly smooth curved cavity surfaces, nothing like what one would expect for the broken surface of sapphire. In addition, we could see the the glass extended across much of the base.
This black star sapphire from Chanthaburi, Thailand has large pits on the base filled with a brown dopping varnish. Long wave ultraviolet light shows the varnish fluoresces orange. Note the pits on the surface of the varnish where gas bubbles were cut through.
This black star sapphire from Chanthaburi, Thailand has large pits on the base filled with a brown dopping varnish. Long wave ultraviolet light shows the varnish fluoresces orange.
This black star sapphire from Chanthaburi, Thailand has large pits on the base filled with a brown dopping varnish. Careful examination reveals gas bubbles trapped in the varnish.
This black star sapphire from Chanthaburi, Thailand has large pits on the base filled with a brown dopping varnish.
In yellow sapphire from Chanthaburi, Thailand, a thin layer of iron-rich silk is typically found in green layers on the skin of the crystal. After cutting, it is commonly seen just under the table and/or culet.

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Thai sapphire inclusions may include mineral crystals, healed fissures, fluid inclusions, negative crystals, growth features and other internal features formed during or after crystal growth. Such features are important to gemologists because they can provide evidence useful in identifying sapphire and evaluating a possible Thai origin.

Thai Sapphire Inclusion Photomicrographs

The Hyperion Thai sapphire gallery includes microscopic features documented in sapphires from Thailand and the Thailand–Cambodia border region. Each entry is accompanied by descriptive information and, where available, references to the gemological literature.

What Inclusions Can Reveal About Thai Sapphire

Inclusions are an important part of geographic origin determination in sapphire. Their form, composition, orientation and associations can provide evidence that, when considered together with other gemological properties, may support or contradict a Thai origin.

Hyperion combines inclusion photomicrography with supporting gemological information so that individual features can be compared with documented examples from Thai sapphires.

About Hyperion

Hyperion is the Lotus Gemology searchable inclusion database. It allows users to browse gemstone inclusions by gem type, geographic origin, treatment and keyword.