igneous

Obsidian Arrowhead

Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)

Hardness: 5-5.5 Mohs scale; Color: Jet black to dark grey; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: None (has Conchoidal fracture); Specific Gravity: 2.4

Hardness: 5-5
Color: Jet black to dark grey
Luster: Vitreous/Glassy

Identified March 13, 2026More igneous →

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Physical properties

Hardness: 5-5.5 Mohs scale; Color: Jet black to dark grey; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: None (has Conchoidal fracture); Specific Gravity: 2.4

Formation & geological history

Formed through the rapid cooling of felsic lava, which prevents crystal growth. This specimen has been shaped by 'knapping' (pressure flaking). Primarily found in volcanic regions from the Pliocene to Holocene epochs.

Uses & applications

Historically used for hunting weaponry and cutting tools. Modern uses include surgical scalpel blades, decorative jewelry, and historical artifacts for collectors.

Geological facts

Obsidian fractures with edges that are thinner and sharper than high-quality steel scalpels. Ancient cultures traded it over thousands of miles as a premium material for tools.

Field identification & locations

Identify in the field by its distinct glass-like sheen, razor-sharp translucent edges, and curved (conchoidal) ripple patterns where it has been chipped. Found in volcanic fields like those in Oregon, Mexico, or Iceland.

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