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Opal · Variety of Opal

Crystal Opal

Transparent to semi-transparent body with vivid spectral play-of-color

Colorless
Optical properties

Optical characteristics

Ref. index
1.37 – 1.47
Luster
Vitreous to waxy
Pleochroism
None None.
Fluorescence
Variable; typically green or white fluorescence under SW UV.
Origins

Source localities

Australia Australia: Lightning Ridge
Premium ★ Top Source

Legendary source of black opal; also produces fine crystal opal.

30% est. supply
Australia Australia: Queensland opal fields
Major

Important boulder opal source; also yields crystal opal.

28% est. supply
Australia Australia: New South Wales / Queensland fields
Significant

Commercial sapphire and opal source; many darker blue to blue-green sapphires.

25% est. supply
Ethiopia Ethiopia: Wollo / Shakiso / emerald fields
Major

Major modern source for opal and emerald.

17% est. supply
Treatments

Enhancement & treatment

Assembled Assembled Stones, Doublets and Triplets Assembled stones combine separate materials to imitate a single gem or enhance appearance. They… Color Enhancement Smoke Treatment Smoke treatment darkens opal body color to imitate black opal or improve contrast. It…
Inclusions

Inclusions & features

Clouds Pinpoint Clouds Under 10x loupe: concentrations of extremely tiny bright dots that individually are too small… Fractures Feathers and Fractures Under 10x loupe: irregular internal surfaces that catch light and appear bright, wing-like, or… Multiphase Two-Phase Inclusions Under 10x loupe: a transparent irregular cavity containing both a liquid phase and a…
Identification

Instruments used

10x Loupe Your most-used instrument, start every examination here Refractometer Measures refractive index, the backbone of gem identification Hydrostatic Scale Measures specific gravity, works even on opaque stones UV Lamp, Long Wave and Short Wave Fluorescence exposes treatments, synthetics, and origin High CRI Penlight Tiny concentrated white spot for field checks, inclusions, fire, and fractures