by AIGS
Needle-like and cuneiform (wedge-shaped) rutile inclusions are a classic internal feature of unheated rubies from Mogok, Myanmar. Formed during crystal growth, these rutile crystals reflect the natural geological conditions under which the ruby developed.
In unheated stones, rutile silk commonly appears intact—fine needles or isolated wedges preserved within the corundum host. Their presence, morphology, and orientation provide valuable evidence for natural origin and lack of heat treatment, as heating typically alters or dissolves rutile structures.
For the experienced gemologist, such inclusions are not flaws but diagnostic markers, offering insight into both the ruby’s formation environment and its treatment history. In Mogok rubies, rutile silk remains one of the most trusted indicators of natural, untreated material.
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