Comparison · Igneous Rocks
Basaltic Andesite vs Phonolite
Basaltic Andesite and Phonolite 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 Basaltic Andesite and Phonolite
- Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Basaltic Andesite leaves a gray to dark gray streak on unglazed porcelain, Phonolite leaves light gray to white.
- They overlap in gray, black, and brown, but Basaltic Andesite also comes in red and Phonolite also comes in green and white.
Basaltic Andesite vs Phonolite properties
| Property | Basaltic Andesite | Phonolite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6 | 6 |
| Luster | dull | dull |
| Streak | Gray to dark gray | Light gray to white |
| Transparency | opaque | opaque |
| Specific gravity | 2.85 | 2.6 |
| Crystal system | varies | varies |
| Common colors | Dark gray, Black, Brown, Red brown, Gray | Gray, Greenish gray, Brown, Black, White |
| Rarity | common | uncommon |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Basaltic Andesite and Phonolite trade in a similar range, around $10.
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.
About Phonolite
Phonolite is an alkali-rich volcanic rock, often gray to greenish gray and fine-grained. Some pieces ring when struck, which inspired the name.
Basaltic Andesite vs Phonolite FAQ
Is Basaltic Andesite the same as Phonolite?
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 Basaltic Andesite from Phonolite?
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Basaltic Andesite leaves a gray to dark gray streak on unglazed porcelain, Phonolite leaves light gray to white. They overlap in gray, black, and brown, but Basaltic Andesite also comes in red and Phonolite also comes in green and white.
Which is harder, Basaltic Andesite or Phonolite?
They are about equally hard, both near Mohs 6.
Which is more valuable, Basaltic Andesite or Phonolite?
Typical specimens of Basaltic Andesite and Phonolite trade in a similar range, around $10.
