Spinel Inclusions

First Published: 7 September 2026

Spinel Inclusions

Explore spinel inclusions in Hyperion, the Lotus Gemology inclusion database. Hyperion contains photomicrographs of inclusions and internal features in natural spinel, documented with information on geographic origin, treatment, lighting conditions, field of view, photographer and published references.

A crystal with sub-inclusions is suspended in this spinel from Mozambique. Micro Raman identified the larger crystal as forsterite and the sub-inclusions as phlogopite.
Small iridescent hexagonal crystals and strings of irregular particles are visible in this pink spinel from Mozambique.
The euhedral crystal in this spinel displays a beautiful iridescent surface.
Parallel bands of fine dislocation needles decorate the interior of this spinel. Vietnamese spinels often contain these types of inclusions.
When magnified, tiny octahedra can be observed forming a fine fingerprint in this spinel. These reflect the underlying symmetry of the spinel crystal.
Within this heated red spinel from the Mahenge region of Tanzania, lies a large crystal (possibly apatite or a carbonate) that exhibits signs of heat damage, specifically the frosted appearance; attached to the crystal is an iridescent plane of thin-films. Additionally, fine remnants of partially dissolved silk (likely högbomite) are scattered across the stone.
Clouds of silk in elongated needles and shorter, finer needles create a misty appearance in this spinel.
The heat treatment of spinel is quite rare, but not unknown and most of the stones are of a purplish red color. Here we see heat-damaged crystals in a Burma spinel. The best way to identify heat treatment in spinel is generally via the photoluminescence (PL) spectrum, rather than inclusions.
When a gem is heated, it and everything contained in it expands, governed by each material’s coefficient of thermal expansion. Should an included crystal expand more than the host, the result is a tension fissure, such as this around a heated apatite crystal in Burma red spinel.
Silk/needles in Tanzania red spinel. Spinels from Tanzania’s Mahenge area often show a turbid appearance due to fine exsolved particles; in less common cases, actual needles can be seen. A fingerprint inclusion is also shown.
While still rare in the market, some spinels are heat treated. We identified that this stone was heated through a combination of the PL (photoluminescence) spectrum and the inclusions, which show signs of melting.
While still rare in the market, some spinels are heat treated. We identified that this stone was heated through a combination of the PL (photoluminescence) spectrum and the inclusions. In this case, the dotted planes that we see may be remnants of the oriented lamellae sometimes seen in Tanzanian spinel.

Spinel 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 spinel, understanding its geological history, recognizing treatment and, in some cases, determining geographic origin.

Spinel Inclusion Photomicrographs

The Hyperion spinel gallery includes microscopic features found in spinels from major deposits around the world. Each entry is accompanied by descriptive information and, where available, references to the gemological literature.

What Inclusions Can Reveal About Spinel

Inclusions are an important part of spinel identification. Their form, composition and alteration can help gemologists distinguish natural spinel from synthetic material, recognize evidence of treatment, and study the geological environment in which the spinel formed.

Hyperion combines inclusion photomicrography with supporting gemological information so that individual features can be compared with documented examples from known spinel deposits.

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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