Iceland spar
Double-refracting crystal
Iceland spar is a transparent variety of calcite notable for its strong double refraction—objects viewed through it appear doubled.
The mineral cleaves into rhombohedral crystals and was historically important in optical instruments, particularly for producing polarized light.
Originally found in large quantities in Iceland, hence the name.
Light splits into two paths
- polarizationSeparation into opposing extremes
- refractionWave bending between media
- opticsScience of illumination
- HuygensSeventeenth-century Dutch astronomer
Fresnel · anisotropy · wavefront · dispersion · interference · wavelength · spectrum · monochromatic
Medieval Scandinavian seafarers
- sunstoneReflective inclusion-bearing feldspar
- NorseAncient Scandinavian civilization
- seafaringTraveling by ocean vessel
- Erik the RedNorse Greenland colonizer
Leif Erikson · sagas · longships · Vinland · Greenland · Scandinavia · wayfinding · overcast
Crystalline calcium carbonate
- carbonateAdd dissolved gas
- rhomboidTilted parallelogram, unequal sides
- aragoniteCalcium carbonate crystal form
- dolomiteCalcium magnesium carbonate mineral
limestone · marble · travertine · chalk · magnesite · siderite · malachite · azurite
Split in hard material
- splittingDividing into parts
- partingAct of leaving another
- separationState of being apart
- cleaveSplit or adhere
lamination · angles · geometry · facets
double refraction
Light splits into two paths
- polarizationSeparation into opposing extremes
- refractionWave bending between media
- opticsScience of illumination
Huygens · Fresnel · anisotropy · wavefront · dispersion · interference · wavelength · spectrum · monochromatic · prism
Vikings
Medieval Scandinavian seafarers
- sunstoneReflective inclusion-bearing feldspar
- NorseAncient Scandinavian civilization
- seafaringTraveling by ocean vessel
Leif Erikson · Erik the Red · sagas · longships · Vinland · Greenland · Scandinavia · wayfinding · overcast · zenith
calcite
Crystalline calcium carbonate
- carbonateAdd dissolved gas
- rhomboidTilted parallelogram, unequal sides
- aragoniteCalcium carbonate crystal form
dolomite · limestone · marble · travertine · chalk · magnesite · siderite · malachite · azurite · mineralogy
fracture
Split in hard material
- splittingDividing into parts
- partingAct of leaving another
- separationState of being apart
cleave · lamination · angles · geometry · facets
transparent
Allowing light through
glassy · colorless · gem-quality · flawless · lustrous · vitreous
- calcitecalcite
- polarized opticsdouble refraction, polarized light, polarizer, analyzer, polarization