igneous
Black glassy volcanic rock, likely scoria or obsidian
Vesicular basaltic scoria (probable); possibly dark obsidian
AI-generated identification · may be incorrectBlack to dark brown, vitreous-to-dull luster, irregular fracture, and apparent vesicles or weathering pits; likely hardness about 5–6, with no obvious cleavage. The image is insufficient to distinguish scoria from obsidian confidently.
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Physical properties
Black to dark brown, vitreous-to-dull luster, irregular fracture, and apparent vesicles or weathering pits; likely hardness about 5–6, with no obvious cleavage. The image is insufficient to distinguish scoria from obsidian confidently.
Formation & geological history
An extrusive igneous material formed when basaltic lava cooled rapidly; scoria forms from gas-rich froth, whereas obsidian forms from silica-rich lava. Commonly Quaternary to Recent volcanic material.
Uses & applications
Scoria is used as lightweight aggregate, landscaping stone, and abrasive; obsidian is used decoratively and occasionally for tools or jewelry. This small beach-worn specimen has modest commercial value.
Geological facts
Its rounded, beach-worn surface and dark glassy appearance are consistent with transported volcanic rock, but industrial slag is also a possible non-geological look-alike.
Field identification & locations
Check for lightweight vesicles, a reddish-brown interior, and basaltic grains for scoria; uniform glass and sharp conchoidal fracture suggest obsidian. Common sources include volcanic coasts and cinder cones.
