RocksdayRhyolite vs Trachyte
How to tell them apart
The volcanic twin of granite — same chemistry, but erupted and cooled fast, so its crystals are tiny.
Photo: Benhoff, CC BY-SA 3.0
A pale volcanic rock rich in alkali feldspar, with a rough feel (its name means 'rough').
Photo: Joseph H. Hartman, CC0
Key differences
- Rhyolite contains quartz.
Side by side
| Property | Rhyolite | Trachyte |
|---|---|---|
| Type | Igneous rock | Igneous rock |
| Mohs hardness | 6–6.5 | 6 |
| Luster | Dull | Dull |
| Colors | Pink, Gray, Brown, Red | Gray, White, Brown |
| Crystal system / structure | Fine-grained, often flow-banded | Fine-grained, aligned feldspar |
| Specific gravity | 2.4–2.6 | 2.4–2.6 |
| Found in | Yellowstone, Wyoming; Owyhee region, Oregon | Drachenfels, Germany; Euganean Hills, Italy |
Properties that are the same for both are grayed out.
How to identify rhyolite
- Light pink, tan or gray.
- Fine-grained, often with swirling flow bands.
- May have small visible quartz or feldspar crystals.
- Lighter in color and weight than basalt.
Structure: Fine-grained, often flow-banded
Full Rhyolite guide →How to identify trachyte
- Light gray to tan, rough to the touch.
- Small aligned feldspar laths.
- Little or no quartz.
Structure: Fine-grained, aligned feldspar
Full Trachyte guide →More comparisons
Could you tell them apart from a blurry close-up?
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