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.

Milkiness, sharp color zone, RC/PT and negative crystals forming fingerprints in E Africa ruby, often confused with Himalayan Arc. Such fine milky clouds (with no visible particles under standard magnification), while found in Vietnam and Afghan rubies, are not found in Mogok stones.
Rose channels are often confused with rutile silk in corundum, but they are easily distinguished as they run in entirely different crystallographic directions. Rutile silk unmixes in three intersecting directions (60/120°) parallel to the faces of the hexagonal prism in the plane of the basal pinacoid. In contrast, Rose channels form parallel to the edges of the rhombohedron, in three directions, but only two in the same place. They intersect at 86.1/93.9°. This ruby from Kiteto, Tanzania shows nice examples.
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 mica crystal in this heated Mozambique ruby.
When a gem is heated, certain inclusion may dissolve or melt. In this case, it appears that the white crystals have dissolved/melted, creating a dendrite-like healing pattern in the surrounding fissure. Also visible are clusters of small crystals of what is probably zircon.
The silk in many East African rubies is not pure rutile, but contains an Fe component, creating tiny daughter crystals at the broad end of the rutile twins. These tiny daughter crystals are more heat-sensitive than the rutile, often developing mottled spots after heat treatment. That is not present in this stone, suggesting it is unheated.
Cube-shaped white crystals with glassy fissures around them in a heated ruby. Crystals such as this with sharp, angular shapes will often produce fissures such as this when heated (moreso than a rounded crystal).
This Mong Hsu ruby contained very fine “silk” needles, likely rutile. These kinds of needles are seem extremely rarely in stones from Mong Hsu. Note that while the needles here are intact, the stone was heated at “low temperature.”
Wispy, cottony diaspore silk, as depicted here, is a common inclusion in rubies from Myanmar’s Mong Hsu mines.
The hexagonal zones in this ruby display a characteristic chalky fluorescence in short wave UV. This is typical in heated Mong Hsu rubies. Prior to heat treatment, the hexagonal core of the crystal is typically blue. Heat treatment removes the blue cores, but also alters the exsolved diaspore particles, and changes the infrared spectrum, assisting detection.
Angular milky texture clouds in a ruby from Rolela, Kiteto, Tanzania.
Spiral fissures amidst milky clouds in an unheated ruby from Rolela, Kiteto, Tanzania.
Rounded bluish crystals of what is probably amphibole in a ruby from Rolela, Kiteto, Tanzania.

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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