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.

Nigeria sapphire; heated; crystal of what is probably rutile breaking the surface
An orange rutile crystal polished through the surface of this sapphire from Nigeria.
Certain type of solid inclusions are heat sensitive and may alter when the gem is heat treated. Here we see crystals that have altered into “snowball” like forms. In addition, the coefficient of thermal expansion of the included crystals was greater than corundum. Thus when heated, they expanded more than the surrounding sapphire, producing glassy discoid fissures.
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.
Heat-altered “snowball” like crystals in a heat-treated sapphire from Sri Lanka.
Heat-altered fingerprints in a heat-treated Ceylon sapphire. Close examination reveals microscopic fractures around each negative crystal, due to the heat treatment.
Rutile consists of titanium dioxide. When a sapphire containing exsolved rutile silk is heated, the rutile melts, sending the titanium back into solution, coloring the stone blue around the now partially dissolved silk. This creates a classic “inkspot” internal diffusion pattern, and is proof of high-temperature heat treatment.
Internal diffusion in heat-treated Ceylon sapphire. This is caused by the bleeding of titanium into the surrounding sapphire from titanium-bearing inclusions such as rutile during high-temperature heat treatment.
Glassy “discoid” inclusions in a heat-treated sapphire from Sri Lanka.
Glassy “discoid” inclusions in a heat-treated sapphire from Sri Lanka.
Glassy “discoid” inclusions in a heat-treated sapphire from Sri Lanka.
Glassy “discoid” inclusions in a heat-treated sapphire from Sri Lanka.

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.

Search the Complete Hyperion Database