Comparison · Igneous Rocks
Basalt vs Basaltic Andesite
Basalt and Basaltic Andesite are easy to confuse because both are igneous rocks. Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Basalt and Basaltic Andesite
- Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Basalt leaves a variable; test individual minerals streak on unglazed porcelain, Basaltic Andesite leaves gray to dark gray.
- They overlap in black and gray, but Basalt also comes in green and Basaltic Andesite also comes in brown and red.
Basalt vs Basaltic Andesite properties
| Property | Basalt | Basaltic Andesite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6 | 6 |
| Luster | dull | dull |
| Streak | Variable; test individual minerals | Gray to dark gray |
| Transparency | opaque | opaque |
| Specific gravity | 3 | 2.85 |
| Crystal system | varies | varies |
| Common colors | Black, Dark Gray, Dark Green | Dark gray, Black, Brown, Red brown, Gray |
| Rarity | common | common |
| Typical specimen value | $1–$30+ | $1–$75+ |
Which is more valuable?
Basaltic Andesite is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Basalt, and premium Basaltic Andesite can reach $75 or more.
About Basalt
Basalt is a dark, fine-grained volcanic rock that makes up most of the ocean floor and Hawaiian Islands. It often forms distinctive columnar jointing.
About 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.
Basalt vs Basaltic Andesite FAQ
Is Basalt the same as Basaltic Andesite?
No. Both are igneous rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Basalt from Basaltic Andesite?
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Basalt leaves a variable; test individual minerals streak on unglazed porcelain, Basaltic Andesite leaves gray to dark gray. They overlap in black and gray, but Basalt also comes in green and Basaltic Andesite also comes in brown and red.
Which is harder, Basalt or Basaltic Andesite?
They are about equally hard, both near Mohs 6.
Which is more valuable, Basalt or Basaltic Andesite?
Basaltic Andesite is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Basalt, and premium Basaltic Andesite can reach $75 or more.
