igneous
Basalt (Vesicular and Ropey)
Vesicular Basalt / Pahoehoe Basalt
Hardness: 5-6 (Mohs scale); Color: Dark grey, black, or reddish-brown due to oxidation; Luster: Dull/Earthy; Structure: Vesicular (pitted with gas bubbles) and ropey (Pahoehoe) texture; Specific Gravity: 2.8–3.0.
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark grey, black, or reddish-brown due to oxidation
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark grey, black, or reddish-brown due to oxidation; Luster: Dull/Earthy; Structure: Vesicular (pitted with gas bubbles) and ropey (Pahoehoe) texture; Specific Gravity: 2.8–3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava (basaltic) erupted from a volcano. The holes (vesicles) are created by trapped gas bubbles. The ropey texture indicates a flow that had a low viscosity.
Uses & applications
Used in landscaping (lava rocks), as an ingredient in concrete, for road base, and as high-quality stone for grilling or sauna heat retention.
Geological facts
Basalt is the most common rock in Earth's crust and makes up most of the ocean floor. The ropey texture shown in parts of this specimen is called Pahoehoe, a Hawaiian term meaning 'smooth, unbroken lava'.
Field identification & locations
Identify by its dark color, heavy weight (relative to size, unless extremely vesicular), and the presence of small holes or flow patterns. Commonly found in volcanic fields like those in Hawaii, Iceland, or the Pacific Northwest.
