Kyanite | Gemopedia

Kyanite is named for the Greek word for blue, kyanos. And what a blue! Fine Nepali kyanite can resemble the finest sapphire. Kyanite was a gem far better known to mineral collectors until more recent finds in the Kali Gandaki river region of west central Nepal, the first source to produce a significant amount of facet grade kyanite. Prior to the Nepal discoveries, Brazil was a major source of mineral specimen material, but kyanite also occurs in a variety of locations around the world. More recent kyanite discoveries have yielded additional colors, including orange and green.
Alternate
Names
Cyanite Or Disthene
Colors
Light To Dark Blue To Green; Zoned With Blue, Green, Colorless Bands

Kyanite Classification

Common Name

Kyanite

Species

Kyanite

Variety

Colors

Light To Dark Blue To Green; Zoned With Blue, Green, Colorless Bands

Alternate Names

Cyanite Or Disthene

Gemstone Groups

Key Separations

refractive index, birefringence, optic character (kyanite is biaxial positive, it has been misstated as biaxial negative) and appearance.

Comments

Fibrous structure rarely produces Cat's-eye stones.

Kyanite Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.716-1.731
Tolerance:(+0.004/-0.004)

Birefringence

0.012-0.017

Optic Character

Biaxial

Optic Sign

Positive

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Weak red
LWUV: Weak red

CCF Reaction

Pleochroism

Trichroic, moderate to strong colorless, dark blue, and violet-blue

Dispersion

Strength: moderate fire Value: 0.02

Comments

Kyanite Chemistry & Crystallography

Chemical Name

aluminum silicate

Chemical Formula

Al2SiO5

Synthesis

Crystal System

Triclinic

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Kyanite Characteristic Physical Properties

Hardness

5.5-7

Streak

White

Specific Gravity

3.56-3.69 Range:0.01/-0.12 Typical:3.68

Toughness

Poor

Inclusions

Kyanite displays color zoning often in bands and may appear fibrous. Stones may contain natural inclusions.

Luster

Vitreous

Stability

Fracture

Uneven

Cleavage

Perfect, in one direction, Good, in two directions

Comments

GEMSTONE SPECTRA
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