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Labradorite  (variety of Feldspar)
Current inventory:  0 gems
 

Chemistry:  (Ca,Na)Al(Al,Si)Si₂O₈

Discovered in 1780;   IMA status: Not Valid (pre-IMA; Grandfathered).
Labradorite is named after the location of its first discovery on Pauls Island, off the coast of Labrador, Canada. Feldspar is named from the Swedish feldt + spat meaning that it was found in fields overlying granite.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/J.07-50

Nickel-Strunz 10th Ed. ID:

9.FA.35

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H₂O
A : Tektosilicates without additional non-tetrahedral anions

Related to:

Feldspar Group. A Plagioclase Feldspar. A variety of Anorthite. An intermediate member of the Albite-Anorthite Series.

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Crystals typically thin, tabular along [010], and rhombic in section, to 4 cm. Cleavable, granular, or massive.

Twinning:

Common according to Albite, Pericline, Carlsbad, Baveno, or Manebach laws.

Physical Properties

Cleavage:

[001] Perfect, [010] Good, [110] Distinct

Fracture:

Uneven to Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

6.0 - 6.5

Density:

2.68 - 2.72 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, Yellow, Gray, Grayish White, White, Light Green, Blue, Brown; commonly exhibits iridescence.

Transparency:

Transparent to Translucent

Luster:

Vitreous

Refractive Index:

1.554 - 1.573  Biaxial ( + )

Birefringence:

0.008 - 0.010

Dispersion:

Weak; r > v; 0.012

Pleochroism:

None

Occurances

Geological Setting:

In mafic igneous rocks and anorthosites. Rarer in metamorphic rocks, as amphibolites. As detrital grains in sedimentary rocks.

Common Associations:

Olivine, Pyroxenes, Amphiboles, Magnetite

Type Locality:

Labrador, Canada

Year Discovered:

1780

View mineral photos:

Labradorite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Labradorite is a member of the Plagioclase Feldspars of the Feldspar Group of minerals that also includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone. Labradorite may be best known for the opaque variety with a color play of iridescent colors that includes blues, greens, gold, orange, yellow and purple. The transparent variety ranges in color from colorless to yellow. It occassionally has inclusions of small to microscopic particles of colloidal copper which creates the effect of schiller. Schiller is the reflection of light off the copper particles suspended in the gem. This type of Labradorite with schiller is called Sunstone.

Labradorite is named after the location of its first discovery; Labrador, Canada. Plagioclase is from the Greek meaning oblique cleavage. Feldspar is from the Swedish feldt + spat meaning that it was found in fields overlying granite.
 

  
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