Organic
Jet
Fossilized organic material used as black gem
Black
Optical characteristics
- Ref. index
- 1.64 – 1.68
- Luster
- Velvety to waxy
- Pleochroism
- None Variable depending on transparency, orientation, and variety.
- Fluorescence
- Variable to inert.
Source localities
United Kingdom
United Kingdom: Whitby jet
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★ Top Source
Classic source for Whitby jet.
Turkey
Turkey: Milas / Muğla
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★ Top Source
Important source for color-change diaspore marketed as Zultanite/Csarite.
Spain
Spain: Salamanca / Iberian quartz localities
Notable
Known for quartz and regional gem materials.
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…
Instruments used
Dichroscope
Reveals pleochroism, instantly eliminates singly-refractive stones
Hydrostatic Scale
Measures specific gravity, works even on opaque 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