Aluminum silicate polymorph stable at low pressures. The variety chiastolite shows a distinctive cross-shaped pattern in cross section. Color: Pink, brown, green, gray. Luster: Vitreous. Streak: White. Cleavage: Good in two directions at 89°. Hardness: 7.5. Transparency: Transparent to opaque. Crystal system: Orthorhombic. Chemical formula: Al₂SiO₅. Specific gravity: 3.13-3.16. Formation: Forms during contact metamorphism and low-pressure regional metamorphism of aluminum-rich pelitic rocks. Common geological settings: Spain Andalusia , Brazil, Sri Lanka, USA; found in contact metamorphic aureoles. Common look-alikes and related entries: Sillimanite, Kyanite, Staurolite.
These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.
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GeoMiner
Last updated
2026-03-30T14:36:54.235567+00:00
Review status
Published; not independently peer-reviewed
IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.
Aluminum silicate polymorph stable at low pressures. The variety chiastolite shows a distinctive cross-shaped pattern in cross section.
How can you identify Andalusite?
Compare several properties rather than relying on colour alone. This entry records colour: Pink, brown, green, gray; lustre: Vitreous; streak: White; Mohs hardness: 7.5; cleavage: Good in two directions at 89°; crystal system: Orthorhombic; transparency: Transparent to opaque. Confirm an important identification with additional field tests or qualified laboratory work.
How does Andalusite form?
Forms during contact metamorphism and low-pressure regional metamorphism of aluminum-rich pelitic rocks.
Where is Andalusite commonly found?
Spain Andalusia , Brazil, Sri Lanka, USA; found in contact metamorphic aureoles.
What is Andalusite commonly confused with?
Andalusite may be confused with Sillimanite, Kyanite, Staurolite. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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