igneous

Basalt Pebble

Basalt

Hardness: 6 (Mohs scale); Color: Dark grey to black with possible greenish tint; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Cleavage: None/Irregular; Specific Gravity: 2.8 - 3.0

Hardness: 6 (Mohs scale)
Color: Dark grey to black with possible greenish tint
Luster: Dull/Matte

Identified May 19, 2026More igneous →

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Physical properties

Hardness: 6 (Mohs scale); Color: Dark grey to black with possible greenish tint; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Cleavage: None/Irregular; Specific Gravity: 2.8 - 3.0

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specimen appears water-worn, indicating it was shaped by fluvial or coastal erosion.

Uses & applications

Common basalt is used as construction aggregate, road base, and in concrete. Small rounded pebbles are often used in landscaping, decorative stone, and garden paths.

Geological facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon, Mars, and Venus.

Field identification & locations

Identify by its heavy weight (high density), dark color, and fine-grained texture. It will not react with acid like limestone and is hard enough to scratch glass with effort. Commonly found along volcanic coastlines and riverbeds in tectonic regions.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous