Kornerupine | Gemopedia

With colors ranging from brown to beautiful emerald green to shades of yellow, kornerupine is strongly pleochroic. It often contains tiny rutile and graphite inclusions that lend to chatoyancy and asterism. Because of its extreme rarity, kornerupine is almost strictly a collectors stone.
Alternate
Names
    Prismatine
Colors
Yellowish To Brownish Green, Blue-Green, Yellow, Brown, Colorless

Kornerupine Classification

Common Name

Kornerupine

Species

Kornerupine

Variety

Colors

Yellowish To Brownish Green, Blue-Green, Yellow, Brown, Colorless

Alternate Names

    Prismatine

Gemstone Groups

Key Separations

RI, birefringence, optic character, pleochroism and possible spectrum and fluorescence

Comments

Kornerupine sometimes shows a pseudo-uniaxial figure. Star and cat's-eye stones are rare.

Kornerupine Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.667-1.68
Tolerance:(+0.003/-0.003)

Birefringence

0.012-0.017

Optic Character

Biaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert to strong yellow
LWUV: Inert to strong yellow

CCF Reaction

Pleochroism

Trichroic, strong green, yellow, and red-brown

Dispersion

Strength: moderate fire Value: 0.019

Comments

Kornerupine Chemistry & Crystallography

Chemical Name

magnesium aluminum borosilicate

Chemical Formula

Mg3Al6(Si,Al,B)5O21(OH)

Synthesis

Crystal System

Orthorhombic

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Kornerupine Characteristic Physical Properties

Hardness

6-7

Streak

White

Specific Gravity

3.27-3.35 Typical:3.3

Toughness

Varies

Inclusions

Kornerupine can contain natural inclusions, zircons and needles. Cat's-eye stones will have parallel rutile or graphite fibers.

Luster

Vitreous

Stability

Fracture

Conchoidal

Cleavage

Good, in one direction

Comments

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