Labradorite (labradorescent) | 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.
Alternate
Names
Spectrolite
Colors
Gray To Almost Black With Blue, Green Interference Colors

Labradorite (labradorescent) Classification

Common Name

Labradorite (labradorescent)

Species

Labradorite

Variety

Colors

Gray To Almost Black With Blue, Green Interference Colors

Alternate Names

Spectrolite

Gemstone Groups

Feldspar

Key Separations

Appearance, RI, birefringence, optic character and magnification

Comments

Stones display labradorscence or blue and green interference colors.Spectrolite is the trade name for labradorite from Finland and has rainbow labradorscence.

Labradorite (labradorescent) Optical Properties

Transparency

Translucent - Opaque

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

None

Dispersion

Comments

Labradorite (labradorescent) 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 (labradorescent) Characteristic Physical Properties

Hardness

6-6.5

Streak

White

Specific Gravity

2.65-2.75 Typical:2.7

Toughness

Poor

Inclusions

Labradorite might show repeated twinning, black magnetite needle like inclusions, ilmenite, and metallic platelets that might be hematite.

Luster

Vitreous

Stability

Good

Fracture

Uneven, Splintery

Cleavage

Perfect, in two directions

Comments

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