igneous

Gold Sheen Obsidian

Volcanic Glass (SiO2 + Fe3O4 / Gas Inclusions)

Hardness: 5-5.5 on Mohs scale; Color: Black with a golden metallic shimmer; Luster: Vitreous to sub-metallic; Crystal structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.35-2.60

Hardness: 5-5
Color: Black with a golden metallic shimmer
Luster: Vitreous to sub-metallic

Identified March 4, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of silica-rich (felsic) lava where tiny gas bubbles or magnetite micro-crystals are trapped at the surface, creating an optical sheen. Most deposits are relatively young geologically (Cenozoic era).

Uses & applications

Used primarily in lapidary arts for jewelry, beads, and cabochons. Historically used for making sharp tools like scalpels and arrowheads; currently used for decorative carvings and metaphysical collection.

Geological facts

The 'sheen' effect is officially known as aventurescence or chatoyancy. Obsidian is technically not a mineral but a 'mineraloid' because it lacks a regular internal atomic structure.

Field identification & locations

Identify in the field by its glassy texture and conchoidal (shell-like) fracturing; the golden sheen is most visible under direct light. Most common in volcanic regions like Mexico (Jalisco) and the United States (Oregon).

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral