Gemstone profile and identification guide
Adularia
Adularia is a low-temperature orthoclase feldspar variety historically associated with moonstone-type adularescence.
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Overview
Adularia is a low-temperature orthoclase feldspar variety historically associated with moonstone-type adularescence.
Did you know? The name adularia comes from the Adula region of the Swiss Alps.
Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.
Identification
Name: Adularia
Scientific classification: Silicate (Feldspar: Orthoclase/Adularia)
Hardness: 6.25 Mohs
Transparency: transparent
Lustre: vitreous to pearly
Crystal system: Monoclinic
Primary colour: White
Secondary colour: Colorless
Colour family: Whites & Neutrals
Identified by feldspar RI/SG values, monoclinic orthoclase identity, and potential adularescent sheen.
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: 6.25 Mohs
Chemical composition: Potassium aluminum silicate (KAlSi3O8)
Crystal system: Monoclinic
Common locations: Switzerland (Adula Alps, historic), Sri Lanka, India, Madagascar, Myanmar
Learn more: Gem-A gemstone education resources.
Colour Variations
Colorless to white orthoclase feldspar, often with a soft adularescent glow in gem material.
Optical effects: Adularescence
Detailed Gemology
Mineral species: Orthoclase (adularia variety)
Mineral group: Feldspar group
Chemical formula: Potassium aluminum silicate (KAlSi3O8)
Mohs hardness: 6.25
Crystal system: Monoclinic
Lustre: vitreous to pearly
Transparency: transparent
Streak: White
Cleavage: Perfect in two directions
Fracture: Uneven to conchoidal
Specific gravity: 2.55-2.58
Refractive index: 1.518-1.526
Optical phenomena: Adularescence in suitable intergrowth material
Colour range: Colorless, white, cream, pale grey
Common inclusions: Twinning lamellae, veils, fluid inclusions
Geological environment: Hydrothermal veins and alpine fissures
Principal mining regions: Switzerland (Adula Alps, historic), Sri Lanka, India, Madagascar, Myanmar
Important commercial sources: Gem adularia-type material is supplied from Sri Lanka, India, Madagascar, and Myanmar; the name derives from historic Swiss localities
Historical significance: Historically important in feldspar and moonstone nomenclature.
Common treatments: Generally untreated.
Synthetic or imitation forms: Glass imitations of moonstone-like sheen are common.
Common look-alikes: Moonstone, colorless feldspar, opalite glass
Jewellery uses: Used in cabochons and collector feldspar specimens where adularescent sheen is present.
Care recommendations: Moderate hardness and feldspar cleavage require care; avoid impact and ultrasonic cleaning.
Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Adularia.
Formation
Forms in low-temperature hydrothermal and alpine fissure environments, commonly as orthoclase-rich feldspar.
Origin
Gem adularia-type material is supplied from Sri Lanka, India, Madagascar, and Myanmar; the name derives from historic Swiss localities
Uses
Best for: Used in cabochons and collector feldspar specimens where adularescent sheen is present.
Ideal uses: Cabochons and protected jewellery settings emphasizing soft internal sheen.
Care
Moderate hardness and feldspar cleavage require care; avoid impact and ultrasonic cleaning.
Need another candidate? Use advanced gemstone search or return to the identification guide.
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Commonly confused gemstones
Adularia FAQ
How can I identify Adularia?
Compare hardness (6.25 Mohs), crystal system (Monoclinic), colour profile, and lustre (vitreous to pearly) with your sample. Then cross-check related gemstones listed above.
What colour range does Adularia appear in?
Colorless to white orthoclase feldspar, often with a soft adularescent glow in gem material.
Where is Adularia commonly used?
Cabochons and protected jewellery settings emphasizing soft internal sheen.. 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.