Natural Ruby Inclusions

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

Rutile silk with vague blue zones in an untreated Mozambique ruby. Note that where the planes of rutile silk are concentrated, the blue color is absent. This is caused by what inclusion specialist John Koivula has dubbed “chromophore cannibalization.” Rutile consists of titanium dioxide and as it grows it sucks the titanium out of solid solution from the surrounding ruby, cannibalizing (removing) the blue color in the process.
Iron-rich silk seen in reflected light in this ruby from Tanzania’s Umba Valley.
Iron-rich silk seen in transmitted light in this ruby from Tanzania’s Umba Valley.
Rutile silk with vague blue zones in an untreated Mozambique ruby. Note that where the planes of rutile silk are concentrated, the blue color is absent. This is caused by what inclusion specialist John Koivula has dubbed “chromophore cannibalization.” Rutile consists of titanium dioxide and as it grows it sucks the titanium out of solid solution from the surrounding ruby, cannibalizing (removing) the blue color in the process.
Mozambique rubies are recovered from an iron-rich soil, which stains the surface-reaching fissures orange. Heat treatment at just 350°C converts the yellowish limonite, which consists of α-FeO(OH), to reddish hematite, which consists of α-Fe2O3. Unfortunately the strong body color of ruby makes it impossible to see this conversion by color alone, but micro-Raman spectroscopy can sometimes detect the change. Heat treatment also causes these naturally-stained fissures to become white and even begin healing into fingerprints.
Although somewhat uncommon, vague blue color zones are sometimes found in Mozambique rubies. Dealers will often heat-treat such stones to remove the blue color.
Dart-like exsolved rutile silk (high relief) with daughter crystals (lower relief) at the broad ends is a common feature of Mozambique rubies. Heat treatment often produces a breakdown of the daughter crystals, producing white spots or bubbles within the daughter.
Some inclusions in Mozambique rubies are thermally sensitive. Here we find small crystals that have melted. The melted crystal (glass) occupies less volume than the original crystal, resulting in a frozen contraction bubble. A small fingerprint surrounds each melted crystal.
Amphibole rods are a common feature of Mozambique rubies, not surprising since the ruby formed in amphibolite (a metamorphic rock consisting mainly of amphiboles) matrix.
Rutile silk (high relief) with daughter crystals (lower relief) at the broad ends is a common feature of Mozambique rubies. Heat treatment often produces a breakdown of the daughter crystals, producing white spots or bubbles within the daughter.
Glass filling in a surface-reaching cavity in a Mozambique ruby. Note the conchoidal fracture on the glass filling.
A mica crystal with a lovely “rosette” surrounding it graces the interior of this untreated Mozambique ruby from the Montepuez area.

Natural ruby inclusions may include mineral crystals, rutile silk, healed fissures, fluid inclusions, negative crystals, color zoning and other features formed during or after crystal growth. Such features are important to gemologists because they can provide evidence useful in identifying ruby, understanding its geological history, recognizing treatment and, in some cases, determining geographic origin.

Natural Ruby Inclusion Photomicrographs

The Hyperion natural ruby gallery includes microscopic features found in rubies 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 Natural Ruby

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

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