Heated Sapphire Inclusions

First Published: 7 September 2026

Heated Sapphire Inclusions

Explore inclusions in heat-treated sapphire in Hyperion, the Lotus Gemology inclusion database. Hyperion contains photomicrographs of inclusions and internal features in natural sapphires that have been subjected to heat treatment, documented with information on geographic origin, lighting conditions, field of view, photographer and published references.

High-temperature heat treatment has the potential to alter certain types of solid inclusions. Here we see an included crystal that melted during heat treatment, turning into glass. Because a glass takes up less volume than a crystal, the result is a void, in the form of a bubble within the glass.
Pink sapphires from Sri Lanka are routinely heated at relatively low temperatures (>1200°C) to drive off the blue tint. While this rarely changes the inclusions, it can be unmasked by reference to the shortwave ultraviolet fluorescence, which often develops chalky zones, as shown in this stone.
When a rutile-silk containing sapphire (such as this stone from Kanchanaburi, Thailand) is heated, the titanium from the rutile moves into solid solution in the sapphire, coloring the area around the rutile blue, creating a distinctive “ink spot” internal diffusion pattern.
The yellow core of this Sri Lankan sapphire fluoresces orange when illuminated by a strong fiber-optic light.
Heat-altered “snowball” like crystals when viewed in transmitted light in a heat-treated sapphire from Sri Lanka.
The yellow core of this Sri Lankan sapphire will fluoresce orange when illuminated by a strong fiber-optic light.
Heat-altered “snowball” like crystals in a heat-treated sapphire from Sri Lanka.
A heat-altered fingerprint in a heat-treated sapphire from Sri Lanka.
When a fingerprint is heated, the tiny negative crystals that form the fingerprint burst, creating tiny microfractures to release the pressure. This often creates a somewhat frosted appearance, as one can see here.
“Bubbly” melted crystals in a heat-treated sapphire from Sri Lanka.
Heat-altered “snowball” like crystals in a heat-treated sapphire from Sri Lanka.
Glassy “discoid” inclusions in a heat-treated sapphire from Sri Lanka.

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Heat treatment can alter inclusions and other internal features in sapphire. Changes may include modification or dissolution of rutile silk, alteration of mineral crystals, decrepitation of fluid inclusions, changes to healed fissures and the formation of heat-related features. Such evidence can be important in determining whether a sapphire has been heated.

Heated Sapphire Inclusion Photomicrographs

The Hyperion heated sapphire gallery includes microscopic features documented in heat-treated natural sapphires. Each entry is accompanied by descriptive information and, where available, references to the gemological literature.

What Inclusions Can Reveal About Heat Treatment

Microscopic examination is an important part of detecting heat treatment in sapphire. The condition of mineral inclusions, rutile silk, fissures and other internal features can provide evidence of exposure to elevated temperatures. These features are evaluated together with other gemological observations when determining treatment status.

Hyperion combines inclusion photomicrography with supporting gemological information so that heat-related features can be compared with documented examples in treated 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.