Vesicular Basalt with Quartz

Physical Properties

Hardness: 6-7 (Mohs scale), Color: Dark grey to black matrix with white inclusions, Luster: Dull/Earthy (matrix) to Vitreous (quartz), Structure: Vesicular/Aphanitic, Cleavage: None

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the Earth's surface. The holes (vesicles) were formed by gas bubbles trapped in the cooling lava. The white portion is secondary quartz mineral crystallization.

Uses & Applications

Commonly used in construction as aggregate, for road base, or in landscaping (lava rocks). Specimens with interesting inclusions are used for educational or amateur collecting purposes.

Geological Facts

Basalt is the most common rock type on Earth's crust and makes up most of the ocean floor. Vesicular basalt can be light enough to resemble pumice but is much denser.

Field Identification & Locations

Identify by its dark, fine-grained texture and the presence of small holes (vesicles). Commonly found in volcanic regions, such as the Pacific Northwest, Hawaii, or Iceland.

Identified on: 4/30/2026

Mode: Standard