Basaltic Andesite
Basaltic andesite is a dark volcanic rock between basalt and andesite in composition. It can look fine-grained, dark gray to black, and may contain small crystals or vesicles.
Basaltic Andesite properties at a glance
| Type | Igneous Rocks |
|---|---|
| Chemical formula | Intermediate volcanic rock between basalt and andesite |
| Mohs hardness | 6 |
| Luster | dull |
| Streak | Gray to dark gray |
| Cleavage | None to variable by phenocrysts |
| Fracture | Uneven to conchoidal |
| Specific gravity | 2.85 |
| Transparency | opaque |
| Common colors | Dark gray, Black, Brown, Red brown, Gray |
| Rarity | common |
Geology & background
Forms when intermediate lava cools at or near the surface, with composition between basalt and andesite.
Basaltic andesite helps geologists interpret volcanic arcs, lava chemistry, and intermediate magma evolution.
How to identify Basaltic Andesite
- Look for dark gray to black fine-grained volcanic texture.
- Basaltic andesite may show tiny feldspar or pyroxene crystals.
- Vesicles can occur but are not required.
- It is visually between basalt and andesite, so locality and context matter.
Where Basaltic Andesite is found
Reported from multiple igneous terrains worldwide; verify locality against specimen provenance when available.
How much is Basaltic Andesite worth?
| Entry-level specimen | $1 |
|---|---|
| Typical collector specimen | $10 |
| Premium specimen | $75+ |
Basaltic Andesite is usually valued for teaching, field context, locality, texture, color, mineral content, or unusually attractive specimens rather than high gem value.
Common uses
- Field identification
- Volcanic rock comparison
- Education
- Aggregate when suitable
Interesting facts
- Basaltic andesite is common in volcanic arcs and some lava flows.
- It can be hard to separate from basalt or andesite by photo alone.
- Small plagioclase or pyroxene crystals may be visible in a fine groundmass.
Care & safety
Basaltic Andesite can vary in toughness, porosity, vesicles, glass content, and weathering depending on cooling history and mineral mix.
Avoid inhaling dust. Do not cut, grind, or polish unknown igneous rocks without eye protection and a properly rated respirator.
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