Labradorite | Gemopedia

Displaying brilliant pastels and deep golden colors, labradorite features a spellbinding "black rainbow" of color. When appreciating the iridescent play of colors known as labradorescence, observe the strength and intensity by viewing from different angles, as different colors or even a range of colors may be visible from different positions.
Colors
Colorless, Weak Green To Yellowish Green, Yellow, Orange To Brown, Brownish Red, Oregon Material Pale To Pinkish Orange, Pink To Reddish Orange, Red-Orange, Deep Red, Pale Yellow To Orange, Moderate To Strong Green Sometimes Bi-Color

Labradorite Classification

Common Name

Labradorite

Species

Labradorite

Variety

Colors

Colorless, Weak Green To Yellowish Green, Yellow, Orange To Brown, Brownish Red, Oregon Material Pale To Pinkish Orange, Pink To Reddish Orange, Red-Orange, Deep Red, Pale Yellow To Orange, Moderate To Strong Green Sometimes Bi-Color

Alternate Names

Gemstone Groups

Feldspar

Key Separations

RI, birefringence, optic character and magnification

Comments

Labradorite often shows twinning in the polariscope. If stones show aventurescence the variety is sunstone or aventurine feldspar. Oregon material might have a RI of 1.563 to 1.572 and SG of 2.67 to 2.72. Oregon material might be called sunstone even when it does not display aventurescence. Misnomers: Rainbow moonstone

Labradorite Optical Properties

Transparency

Semitransparent - Translucent

Refractive Index

1.559-1.568
Tolerance:(+0.005/-0.005)

Birefringence

0.009

Optic Character

Biaxial

Optic Sign

Positive

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert to weak white
LWUV: Inert to weak white

CCF Reaction

Pleochroism

Dichroic, colorless and light yellow

Dispersion

Comments

Labradorite Chemistry & Crystallography

Chemical Name

calcium or sodium silicate

Chemical Formula

NaAlSi3O8 or CaAl2Si2O8

Synthesis

Crystal System

Triclinic

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Labradorite Characteristic Physical Properties

Hardness

6-6.5

Streak

White

Specific Gravity

2.65-2.75 Typical:2.7

Toughness

Poor

Inclusions

Stones might show repeated twinning, black magnetite needle like inclusions, ilmenite, and metallic platelets that might be hematite. Oregon material will contain tiny orangy yellow copper platelets.

Luster

Vitreous

Stability

Good

Fracture

Uneven, Splintery

Cleavage

Perfect, in two directions

Comments

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