Gemstone profile and identification guide
Iceland Spar
Iceland spar is a transparent variety of calcite noted for pronounced birefringence and double refraction.
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Overview
Iceland spar is a transparent variety of calcite noted for pronounced birefringence and double refraction.
Did you know? Iceland spar played a key role in early optical studies of polarization and birefringence.
Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.
Identification
Name: Iceland Spar
Scientific classification: Carbonate (Calcite Variety)
Hardness: 3 Mohs
Transparency: transparent
Lustre: vitreous
Crystal system: Trigonal
Primary colour: Colorless
Secondary colour: White
Colour family: Whites & Neutrals
Doubling of viewed text through the crystal is the classic identification feature.
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: soft
Hardness value: 3 Mohs
Chemical composition: Calcium carbonate (CaCO3)
Crystal system: Trigonal
Common locations: Iceland, Mexico, China, United States
Learn more: Gem-A gemstone education resources.
Colour Variations
Highly transparent colorless calcite famous for strong double refraction.
Optical effects: Strong Double Refraction
Detailed Gemology
Mineral species: Calcite (Iceland spar variety)
Mineral group: Carbonate group
Chemical formula: Calcium carbonate (CaCO3)
Mohs hardness: 3
Crystal system: Trigonal
Lustre: vitreous
Transparency: transparent
Streak: White
Cleavage: Perfect rhombohedral cleavage in three directions
Fracture: Conchoidal to uneven
Specific gravity: 2.71
Refractive index: 1.486 and 1.658
Optical phenomena: Strong double refraction
Colour range: Colorless to white
Common inclusions: Cleavage planes, growth zoning, fluid inclusions
Geological environment: Hydrothermal veins and carbonate deposits
Principal mining regions: Iceland, Mexico, China, United States
Important commercial sources: Classic Iceland spar is from Icelandic calcite deposits, with similar optical calcite from other countries
Historical significance: Historically central to optical mineralogy and crystallography.
Common treatments: Generally untreated.
Synthetic or imitation forms: Glass does not reproduce the same double refraction behavior.
Common look-alikes: Quartz, glass, optical calcite from other localities
Jewellery uses: Used in optical demonstrations, collector specimens, and occasional ornamental pieces.
Care recommendations: Soft and acid-sensitive; avoid impact, acids, and ultrasonic cleaning.
Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Iceland Spar.
Formation
Forms in hydrothermal veins and sedimentary environments rich in calcium carbonate.
Origin
Classic Iceland spar is from Icelandic calcite deposits, with similar optical calcite from other countries
Uses
Best for: Used in optical demonstrations, collector specimens, and occasional ornamental pieces.
Ideal uses: Collector and educational optical specimens rather than daily jewelry wear.
Care
Soft and acid-sensitive; avoid impact, acids, and ultrasonic cleaning.
Need another candidate? Use advanced gemstone search or return to the identification guide.
Related gemstones by colour
Related gemstones by hardness
Gemstones from the same mineral family
Commonly confused gemstones
Iceland Spar FAQ
How can I identify Iceland Spar?
Compare hardness (3 Mohs), crystal system (Trigonal), colour profile, and lustre (vitreous) with your sample. Then cross-check related gemstones listed above.
What colour range does Iceland Spar appear in?
Highly transparent colorless calcite famous for strong double refraction.
Where is Iceland Spar commonly used?
Collector and educational optical specimens rather than daily jewelry wear.. For maintenance, follow the care guidance in this profile.
Scientific References
GIA: general gemstone identity (reviewed) - Batch 04 factual verification pass.
Gem-A: gemological terminology and testing references (reviewed) - Batch 04 factual verification pass.
Mindat: mineral species and principal localities (reviewed) - Batch 04 factual verification pass.
International Gem Society: gem trade context and treatment overview (reviewed) - Batch 04 factual verification pass.