Comparison · Igneous Rocks
Andesite vs Dacite
Andesite and Dacite are easy to confuse because both are igneous rocks. Dacite is harder (Mohs 6–7) than Andesite (Mohs 5–6), so Dacite will scratch Andesite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Andesite and Dacite
- Dacite is harder (Mohs 6–7) than Andesite (Mohs 5–6), so Dacite will scratch Andesite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
- They overlap in gray and brown, but Andesite also comes in green and black.
Andesite vs Dacite properties
| Property | Andesite | Dacite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 5–6 | 6–7 |
| Luster | Dull groundmass with vitreous phenocrysts | Dull to vitreous |
| Transparency | Opaque | Opaque |
| Specific gravity | 2.5–2.8 | 2.6–2.7 |
| Common colors | Gray, Dark gray, Greenish gray, Brown, Black | Gray, Light gray, Tan, Pale brown |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Andesite and Dacite trade in a similar range, around $10.
About Andesite
Andesite is a fine-grained, intermediate volcanic rock formed from lava with a silica content between basalt and rhyolite, typically 57 to 63 percent. It is named for the Andes Mountains, where it makes up much of the volcanic arc, and its groundmass is usually too fine to identify individual minerals without magnification. Andesite forms at convergent plate boundaries where oceanic crust melts beneath continental or island arcs.
About Dacite
Dacite is a fine-grained, extrusive igneous rock of intermediate to felsic composition, chemically positioned between andesite and rhyolite with roughly 63 to 68 percent silica. It usually shows a porphyritic texture, with visible crystals of plagioclase, quartz, and hornblende or biotite set in a dense, glassy to microcrystalline groundmass. Dacite magma is typically thick and gas-rich, making it prone to explosive eruption.
Andesite vs Dacite FAQ
Is Andesite the same as Dacite?
No. Both are igneous rocks, but they are distinct rock types with different hardness, streak or luster. Dacite is harder (Mohs 6–7) than Andesite (Mohs 5–6), so Dacite will scratch Andesite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
How can you tell Andesite from Dacite?
Dacite is harder (Mohs 6–7) than Andesite (Mohs 5–6), so Dacite will scratch Andesite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. They overlap in gray and brown, but Andesite also comes in green and black.
Which is harder, Andesite or Dacite?
Dacite is harder: Mohs 6–7 against Mohs 5–6 for Andesite.
Which is more valuable, Andesite or Dacite?
Typical specimens of Andesite and Dacite trade in a similar range, around $10.
