Basalt with Granite Inclusions (Xenoliths)

Physical Properties

Hardness: 6-7 on Mohs scale. Color: Dark gray to black (matrix) with light gray/white inclusions. Luster: Dull to sub-metallic. Crystal structure: Aphanitic (fine-grained) matrix with phaneritic (coarse) inclusions. Specific gravity: 2.8-3.0.

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The lighter patches (xenoliths) are older crustal rocks that were trapped in the magma as it rose.

Uses & Applications

Used primarily in landscaping (boulders), road construction (crushed stone), and as decorative garden features.

Geological Facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The lighter sections in these specific boulders are called 'xenoliths' from the Greek words for 'foreign rock'.

Field Identification & Locations

Identify in the field by the high density, dark color, and fine-grained texture of the main body, often showing distinct 'clapping' or lighter mineral veining. Commonly found in volcanic regions.

Identified on: 4/24/2026

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