description Sillimanite Overview
Sillimanite is an aluminium silicate mineral with the chemical formula Al2SiO5, and one of three polymorphs that also include andalusite and kyanite. It forms mainly in metamorphic rocks exposed to high temperatures and is also known as fibrolite when it occurs in fibrous aggregates. Transparent or strongly coloured material can be cut as a gemstone, with gem-quality examples reported from Sri Lanka, Myanmar, and Tanzania.
help Sillimanite FAQ
How good is Sillimanite?
Sillimanite scores 6.42/10 (Fair) on Lunoo, making it rated in the Gemstone category. Durable enough and sometimes attractive in cat's-eye form; low name recognition and limited availability constrain demand.
What are the best alternatives to Sillimanite?
See our alternatives page for Sillimanite for a ranked list with scores. Top alternatives include: Indicolite, Euclase, Phenakite.
How does Sillimanite compare to Indicolite?
See our detailed comparison of Sillimanite vs Indicolite with scores, features, and an AI-powered verdict.
Is Sillimanite worth it in 2026?
With a score of 6.42/10, Sillimanite is a solid option in Gemstone. See all Gemstone ranked.
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