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.

Small crystals with decolorized areas around growth tubes cut through on the surface. The growth tubes have apparently drawn titanium out of solid solution in the sapphire, thus cannibalizing the color.
Angular cloud of particles in sapphire. Such dense “texture clouds” are often a sign of high-temperature heat treatment; FOV~ 7 mm
Sapphires treated with high temperatures and modest pressure (HT+P) sometimes contain ghost-like fingerprints with low relief crystals, when viewed in transmitted light. In crossed polars, these crystals stand out clearly and are birefringent. Using Lotus Gemology’s micro Raman unit, we have identified these crystals as recrystallized corundum.
Sapphires treated with high temperatures and modest pressure (HT+P) sometimes contain ghost-like fingerprints with low relief crystals, when viewed in transmitted light. In crossed polars, these crystals stand out clearly and are birefringent. Using Lotus Gemology’s micro Raman unit, we have identified these crystals as recrystallized corundum.
The fingerprint in this sapphire shows clear signs of heat alteration. Note the frosty, hazy appearance between the negative crystals, which results from micro-fractures to release the pressure caused by heating; also note that each negative crystal tube has begun to neck down and become more rounded.
This cluster of melted crystals with a frosty “snowball” appearance and glassy discoid around them is a clear sign that their sapphire host has been heat treated.
Angular zoned chalky shortwave fluorescent reaction, indicative of heat treatment.
The melted, shiny fissure around this small crystal represents clear evidence that the sapphire host has been heat treated.
Chalky shortwave fluorescence is characteristic of heated sapphire.
A sharply zoned angular particle cloud creates a striking geometric shape next to a large glassy discoid in this heated Sri Lanka sapphire.
This Burmese pink sapphire has an unusual feature: a drilled hole that extends from the surface into a crystal. We suspect this may have been done to clear out any debris inside the crystal with acid cleaning, making the crystal less noticeable.
Chalky shortwave fluorescence follows the pattern of partially dissolved silk in this heated pink sapphire.

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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.