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.

Photomicrography is no different than ordinary photography. It’s all about controlling light. In this case, a nondescript fluid inclusion in dark-field illumination morphed into a spectral spectacular when light was brought from above.
This heat-treated blue sapphire from Sri Lanka featured a corundum crystal included in the sapphire that was cut through on the surface. When viewed between crossed polars, the corundum crystal is brilliantly silhouetted against a dark background.
This heat-treated blue sapphire from Sri Lanka featured a corundum crystal included in the sapphire that was cut through on the surface.
When viewed in shortwave UV illumination, chalky angular zoned clouds of particles become evident. This is a clear sign of heat treatment.
When viewed in shortwave UV illumination, chalky angular zoned clouds of particles become evident. This is a clear sign of heat treatment.
When viewed in shortwave UV illumination, chalky angular zoned clouds of particles become evident. This is a clear sign of heat treatment.
When examined between crossed polars two twin planes can be easily spotted in this sapphire.
Shiny, glassy discoids and frosted crystals display clear evidence that this sapphire was heated.
A zoned, chalky appearance in shortwave UV illumination is a sign of heat treatment in sapphire.
Small glassy discoids embedded in a partially healed fissure provide evidence that this sapphire was heated.
A glassy discoid around a tiny melted crystal provides evidence that this inclusion’s sapphire host has been heated. Specimen courtesy Tristan Knowles.
A “ghost” fissure in a Sri Lankan sapphire treated with high-temperature heating plus pressure (HT+P). In crossed polars, the fissure shows transparent doubly refractive crystals. These have previously been identified as corundum by Lotus gemologists using microRaman. These tiny synthetic corundum crystals form during the treatment. Nathan Renfro of the GIA was the first to notice these ghost crystals. E. Billie Hughes of Lotus Gemology was the first to identify them. FoV=4 mm.

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.

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