igneous
Basalt Arrowhead (worked stone)
Aphanitic mafic volcanic rock (Basalt)
Hardness: 6; Color: Dark grey to black; Luster: Dull/Earthy; Structure: Microcrystalline (aphanitic) with frequent conchoidal fracturing when worked; Specific Gravity: 2.8–3.0.
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6; Color: Dark grey to black; Luster: Dull/Earthy; Structure: Microcrystalline (aphanitic) with frequent conchoidal fracturing when worked; Specific Gravity: 2.8–3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. Basaltic formations can range from modern era back to billions of years old, often found in oceanic crust and volcanic plateaus.
Uses & applications
Used historically by indigenous peoples for stone tools (lithics) such as arrowheads, scrapers, and axes. Modern basalt is used in construction as crushed stone, floor tiles, and as a component in high-strength industrial fibers (basalt fiber).
Geological facts
Basalt is the most common rock type in the Earth's crust and also makes up most of the surface of the Moon and Mars. This specific specimen shows clear signs of 'knapping'—the intentional shaping of stone by human hands in antiquity.
Field identification & locations
Identify in the field by its dark color, heavy weight for its size, and fine-grained texture. To distinguish an artifact from a natural rock, look for 'flake scars' and a sharp, bifacial edge (worked on both sides) resulting from percussion or pressure flaking.
