igneous
Obsidian Arrowhead
Volcanic Glass (Amorphous Silicon Dioxide)
Hardness of 5-5.5 on the Mohs scale, typically black to dark brown in color, vitreous (glassy) luster, amorphous crystal structure with conchoidal fracture, specific gravity of around 2.35 - 2.60
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Physical properties
Hardness of 5-5.5 on the Mohs scale, typically black to dark brown in color, vitreous (glassy) luster, amorphous crystal structure with conchoidal fracture, specific gravity of around 2.35 - 2.60
Formation & geological history
Formed as an extrusive igneous rock when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. Found worldwide where volcanic activity has occurred.
Uses & applications
Historically used for cutting tools, spear points, arrowheads, and blades due to its extremely sharp edges. Currently used in jewelry, decorative items, and occasionally in experimental surgical scalpels.
Geological facts
Obsidian fractures with extremely sharp edges, producing a cutting edge that can be thinner than a nanometer. It has been utilized by humans for toolmaking since the Stone Age.
Field identification & locations
Easily identified by its shiny, black, glass-like appearance and sharp conchoidal fracture edges. Often crafted into arrowheads and artifacts found near volcanic regions.
