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Volcanic Glass

Obsidian

Opaque black; varieties include rainbow, snowflake, and mahogany obsidian

Black
Optical properties

Optical characteristics

Ref. index
1.48 – 1.51
Luster
Vitreous
Pleochroism
None None.
Fluorescence
Inert.
Origins

Source localities

Mexico Mexico: Quer├®taro / Jalisco / Sonora / Coahuila
Significant

Known for fire opal, turquoise, amber and collector minerals; Mexico is also a major obsidian source.

30% est. supply
United States USA: major gem fields
Commercial

Diverse sources for turquoise, tourmaline, opal, sapphire, topaz, red beryl and rare minerals.

25% est. supply
Italy Italy: Val Malenco / alpine localities
Significant

Known for demantoid and collector minerals; Lipari and Sardinia are classic obsidian sources.

15% est. supply
Worldwide Worldwide
Commercial

Broad worldwide occurrence or distribution.

30% est. supply
Inclusions

Inclusions & features

Clouds Pinpoint Clouds Under 10x loupe: concentrations of extremely tiny bright dots that individually are too small…
Identification

Instruments used

10x Loupe Your most-used instrument, start every examination here Hydrostatic Scale Measures specific gravity, works even on opaque stones High CRI Penlight Tiny concentrated white spot for field checks, inclusions, fire, and fractures