Gemstone profile and identification guide
Andalusite
Andalusite is an aluminum silicate gemstone noted for strong pleochroism between green, yellow, and brown hues.
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Overview
Andalusite is an aluminum silicate gemstone noted for strong pleochroism between green, yellow, and brown hues.
Did you know? Andalusite can display striking tricolour appearance when oriented for faceting.
Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.
Identification
Name: Andalusite
Scientific classification: Silicate (Andalusite)
Hardness: 7 Mohs
Transparency: transparent
Lustre: vitreous
Crystal system: Orthorhombic
Primary colour: Green Brown
Secondary colour: Brown
Colour family: Browns
Strong pleochroism and orthorhombic Al2SiO5 identity separate andalusite from many brown/green gems.
Verification Status
Status: verified-core-fields
Reference priority: GIA, Gem-A, Mindat, International Gem Society
Core identity, locality, and physical-property fields reviewed against standard gemological references.
Values are reported as practical gemological ranges where appropriate.
Physical Properties
Hardness category: hard
Hardness value: 7 Mohs
Chemical composition: Aluminum silicate (Al2SiO5)
Crystal system: Orthorhombic
Common locations: Brazil, Sri Lanka, Spain, Tanzania, Madagascar
Learn more: Gem-A gemstone education resources.
Colour Variations
Typically olive-green to brown with strong directional pleochroism.
Optical effects: Pleochroism
Detailed Gemology
Mineral species: Andalusite
Mineral group: Nesosilicate group
Chemical formula: Aluminum silicate (Al2SiO5)
Mohs hardness: 7
Crystal system: Orthorhombic
Lustre: vitreous
Transparency: transparent
Streak: White
Cleavage: Poor
Fracture: Uneven to subconchoidal
Specific gravity: 3.13-3.20
Refractive index: 1.629-1.650
Optical phenomena: Strong pleochroism
Colour range: Olive green, yellow green, brown, reddish brown
Common inclusions: Needles, fluid inclusions, zoning
Geological environment: Regional and contact metamorphic rocks
Principal mining regions: Brazil, Sri Lanka, Spain, Tanzania, Madagascar
Important commercial sources: Commercial facetable andalusite is produced mainly in Brazil and Sri Lanka, with additional East African sources
Historical significance: Known as a collector gemstone for pleochroic performance.
Common treatments: Generally untreated.
Synthetic or imitation forms: Glass and synthetic gems may imitate colour but not pleochroic pattern.
Common look-alikes: Tourmaline, sphene, chrysoberyl
Jewellery uses: Used in faceted gemstones for collectors and jewellery.
Care recommendations: Good durability for jewellery but avoid impact due to directional brittleness and inclusions.
Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Andalusite.
Formation
Forms in metamorphic rocks at low pressure and moderate-high temperature, and in contact aureoles.
Origin
Commercial facetable andalusite is produced mainly in Brazil and Sri Lanka, with additional East African sources
Uses
Best for: Used in faceted gemstones for collectors and jewellery.
Ideal uses: Faceted stones where pleochroic colour shifts are visible.
Care
Good durability for jewellery but avoid impact due to directional brittleness and inclusions.
Need another candidate? Use advanced gemstone search or return to the identification guide.
Related gemstones by colour
Related gemstones by hardness
Commonly confused gemstones
Andalusite FAQ
How can I identify Andalusite?
Compare hardness (7 Mohs), crystal system (Orthorhombic), colour profile, and lustre (vitreous) with your sample. Then cross-check related gemstones listed above.
What colour range does Andalusite appear in?
Typically olive-green to brown with strong directional pleochroism.
Where is Andalusite commonly used?
Faceted stones where pleochroic colour shifts are visible.. For maintenance, follow the care guidance in this profile.
Scientific References
GIA: general gemstone identity (reviewed) - Batch 02 factual verification pass.
Gem-A: gemological terminology and testing references (reviewed) - Batch 02 factual verification pass.
Mindat: mineral species and principal localities (reviewed) - Batch 02 factual verification pass.
International Gem Society: gem trade context and treatment overview (reviewed) - Batch 02 factual verification pass.