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Corundum · Variety of Sapphire

Purple Sapphire

Purple to violet-blue, mixed iron and chromium coloring

Purple Violet
Optical properties

Optical characteristics

Ref. index
1.762 – 1.77
Birefringence
0.008 – 0.01
Luster
Vitreous
Pleochroism
Strong Dichroism from purple to violet-blue or reddish-purple depending on the Fe/Cr ratio.
Fluorescence
Typically weak to inert under UV.
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.

30% est. supply
Myanmar Myanmar: Mogok Valley
Premium ★ Top Source

Classic source for ruby, sapphire, spinel and other collector gems.

14% est. supply
Cambodia Cambodia: Pailin
Significant

Historic source for dark blue sapphire and ruby near the Thai border.

20% est. supply
Tanzania Tanzania: Umba Valley
Significant

Diverse alluvial deposit known for color-change sapphires, Umba padparadscha, rhodolite and malaia garnet.

12% est. supply
Thailand Thailand: Chanthaburi / Kanchanaburi
Commercial

Historic ruby and sapphire area and major cutting/trading center; many stones are heat treated.

15% est. supply
Madagascar Madagascar: Ilakaka / Andranondambo region
Major

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

9% 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… Diffusion Surface Diffusion Surface diffusion adds coloring elements near the surface. It is less durable than body…
Inclusions

Inclusions & features

Zoning Color Zoning Under 10x loupe in immersion: bands or patches of deeper or lighter color arranged… Needles Silk, Rutile Needles Under 10x loupe: extremely fine bright lines crossing in three directions at 60° angles.… Crystals Crystal Inclusions Under 10x loupe: solid, well-formed mineral crystals trapped inside the host gem. They may… Fractures Fingerprint Inclusions Under 10x loupe: curved or wavy lines of tiny dots forming patterns that look… Fractures Feathers and Fractures Under 10x loupe: irregular internal surfaces that catch light and appear bright, wing-like, or… Crystals Negative Crystals Under 10x loupe: an empty cavity that has the geometric shape of the host…
Identification

Instruments used

Refractometer Measures refractive index, the backbone of gem identification Dichroscope Reveals pleochroism, instantly eliminates singly-refractive stones 10x Loupe Your most-used instrument, start every examination here UV Lamp, Long Wave and Short Wave Fluorescence exposes treatments, synthetics, and origin Spectroscope Reads characteristic absorption lines, confirms chromium, iron, copper Polariscope Determines single vs. double refraction, quick and conclusive