igneous
Vesicular Basalt (Amygdaloidal Basalt)
Basalt with Secondary Mineral Inclusions
Hardness: 5-6 (Mohs scale); Color: Dark reddish-brown to black with white spots; Luster: Dull or earthy; Crystal structure: Aphanitic (fine-grained) with vesicles; Specific gravity: 2.8-3.0.
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark reddish-brown to black with white spots
- Luster
- Dull or earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark reddish-brown to black with white spots; Luster: Dull or earthy; Crystal structure: Aphanitic (fine-grained) with vesicles; Specific gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava. The holes (vesicles) were created by escaping gas bubbles, which were later filled with secondary minerals like quartz, calcite, or zeolites (forming amygdules).
Uses & applications
Used in construction as road base, concrete aggregate, and railroad ballast. Minor use as decorative landscape stone or aquarium rocks.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up a large portion of the surfaces of the Moon, Mars, and Venus.
Field identification & locations
Identify in the field by its high density, dark color, and characteristic 'pitted' or 'spotted' appearance. Commonly found in volcanic regions, such as the Pacific Northwest, Hawaii, or the Lake Superior region in the US.
