Ruby (Cat's-Eye) | Gemopedia

The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case ruby. The effect, when present, appears as a bright, narrow slit similar to the pupils in the eyes of your favorite feline. This phenomenon is caused by parallel fibrous or needle-like inclusions that interfere with the passage of light through the crystal, scattering and reflecting light back to the viewer as a thin line.
Colors
Orangy Red To Purplish Red

Ruby (Cat's-Eye) Classification

Common Name

Ruby (Cat's-Eye)

Species

Corundum

Variety

Cat's-Eye Ruby

Colors

Orangy Red To Purplish Red

Alternate Names

Gemstone Groups

Key Separations

Appearance, RI and magnification

Comments

Stone usually cut as cabochons.

Ruby (Cat's-Eye) Optical Properties

Transparency

Semitransparent To Opaque

Refractive Index

1.762-1.77
Tolerance: (+0.009/-0.005)

Birefringence

0.008-0.01

Optic Character

Uniaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Weak to strong red, stronger under SWUV. Slightly weaker than synthetic ruby.Heated ruby might have chalky fluorescence
LWUV: Weak to strong red

CCF Reaction

Pleochroism

Unobservable

Dispersion

Strength: moderate fire Value: 0.018

Comments

Ruby (Cat's-Eye) Chemistry & Crystallography

Chemical Name

aluminum oxide

Chemical Formula

Al2O3

Synthesis

Crystal System

Trigonal

Classification

Oxide

Nature

Natural

Crystallinity

Crystalline

Comments

Ruby (Cat's-Eye) Characteristic Physical Properties

Hardness

9

Streak

White

Specific Gravity

4.1-3.95 Typical: 4

Toughness

Varies

Inclusions

Cat's-eye rubies will have silk or sets of parallel rutile needles, hexagonal growth lines, color zoning, liquid, negative and mineral inclusions. Some stone might show twinning.

Luster

SubAdamantine

Stability

Very Good

Fracture

Conchoidal

Cleavage

None

Comments

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