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Corundum · Variety of Sapphire

Color Change Sapphire

Color changes between daylight and incandescent light, often blue/purple to violet/red-purple

Color Change
Optical properties

Optical characteristics

Ref. index
1.762 – 1.77
Birefringence
0.008 – 0.01
Luster
Vitreous
Pleochroism
Strong Strong and combined with color-change effect.
Fluorescence
Variable.
Origins

Source localities

Sri Lanka Sri Lanka: Ratnapura / Elahera
Premium ★ Top Source

Classic Ceylon source for sapphire and many alluvial gems; known for bright colors and good clarity.

32% est. supply
Tanzania Tanzania: Merelani Hills
Major

Major source for tanzanite, garnet, spinel, tourmaline, ruby and fancy sapphires.

22% est. supply
Myanmar Myanmar: Mogok Valley
Premium ★ Top Source

Mogok produces fine color-change sapphires with strong blue-to-violet shifts.

8% est. supply
India Kashmir: Zanskar Range
Legendary ★ Top Source

Rare color-change sapphires occur in Kashmir alongside the classic blue material.

1% est. supply
Tanzania Tanzania: Umba Valley
Premium

Umba Valley known for color-change sapphires shifting from blue-green to purplish-red.

11% est. supply
Madagascar Madagascar: Ilakaka / Andranondambo region
Major

Modern major source for sapphire, garnet, beryl, quartz, tourmaline and many collector gems.

26% est. supply
Treatments

Enhancement & treatment

Heat Heat Treatment, Corundum Heat is the most common corundum treatment. It can improve color and clarity, but… Diffusion Beryllium Diffusion Beryllium diffusion introduces light elements during high-temperature heating to alter body color. It must… Clarity Enhancement Flux Healing, Corundum Flux healing uses high temperature and flux to partially heal fractures in corundum. It… Clarity Enhancement Fracture Filling, Corundum Fracture filling improves apparent clarity in corundum. Lead-glass-filled ruby is the most important commercial…
Inclusions

Inclusions & features

Zoning Color Zoning Under 10x loupe in immersion: bands or patches of deeper or lighter color arranged… Crystals Crystal Inclusions Under 10x loupe: solid, well-formed mineral crystals trapped inside the host gem. They may… Synthetic Curved Growth Striae, Synthetic ID Under 10x loupe in immersion: curved parallel lines flowing through the stone in sweeping… Fractures Feathers and Fractures Under 10x loupe: irregular internal surfaces that catch light and appear bright, wing-like, or… Fractures Fingerprint Inclusions Under 10x loupe: curved or wavy lines of tiny dots forming patterns that look… Crystals Negative Crystals Under 10x loupe: an empty cavity that has the geometric shape of the host… Clouds Pinpoint Clouds Under 10x loupe: concentrations of extremely tiny bright dots that individually are too small… Needles Silk, Rutile Needles Under 10x loupe: extremely fine bright lines crossing in three directions at 60° angles.… Multiphase Two-Phase Inclusions Under 10x loupe: a transparent irregular cavity containing both a liquid phase and a…
Identification

Instruments used

Dichroscope Reveals pleochroism, instantly eliminates singly-refractive stones Immersion Microscope See every internal detail clearly, the professional standard 10x Loupe Your most-used instrument, start every examination here Polariscope Determines single vs. double refraction, quick and conclusive Refractometer Measures refractive index, the backbone of gem identification UV Lamp, Long Wave and Short Wave Fluorescence exposes treatments, synthetics, and origin