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Spinel · Variety of Spinel

Cobalt Blue Spinel

Vivid saturated blue, cobalt to electric blue

Blue
Optical properties

Optical characteristics

Ref. index
1.712 – 1.736
Luster
Vitreous
Pleochroism
None (isotropic)
Fluorescence
Inert to weak blue (LW)
Origins

Source localities

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

Sri Lanka is the primary source of gem-quality cobalt-blue spinel; deep 'cornflower' blue stones from Ratnapura are benchmark quality.

45% est. supply
Myanmar Myanmar: Mogok Valley
Major

Mogok yields occasional cobalt-blue spinel alongside its classic red and pink material.

20% est. supply
Vietnam Vietnam: Luc Yen / Quy Chau
Premium ★ Top Source

Vietnam's Luc Yen district produces cobalt-blue spinel of exceptional saturation, sometimes rivaling the finest Sri Lankan material.

35% est. supply
Inclusions

Inclusions & features

Crystals Crystal Inclusions Under 10x loupe: solid, well-formed mineral crystals trapped inside the host gem. They may… 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… Clouds Pinpoint Clouds Under 10x loupe: concentrations of extremely tiny bright dots that individually are too small… 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 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