Comparison · Igneous Rocks
Pumice vs Rhyolite
Pumice and Rhyolite are easy to confuse because both are igneous rocks. Both sit near Mohs 5–6, 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 Pumice and Rhyolite
- Both sit near Mohs 5–6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Rhyolite feels noticeably heavier for its size (specific gravity 2.35–2.7 versus 0.25–0.9 for Pumice).
- Hold a thin edge to the light: Pumice is Opaque, translucent in thin shards, Rhyolite is Opaque.
- They overlap in white, gray, and brown, but Pumice also comes in yellow and Rhyolite also comes in pink, red, and multicolored.
Pumice vs Rhyolite properties
| Property | Pumice | Rhyolite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 5–6 | 5.5–7 |
| Luster | Dull to glassy | Dull to vitreous (glassy groundmass) |
| Transparency | Opaque, translucent in thin shards | Opaque |
| Specific gravity | 0.25–0.9 | 2.35–2.7 |
| Crystal system | Amorphous | — |
| Common colors | White, Light gray, Tan, Pale yellow | Pink, Gray, Tan, Red, White, Banded |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Pumice and Rhyolite trade in a similar range, around $10.
About Pumice
Pumice is a light-colored, extrusive volcanic rock so full of trapped gas bubbles, or vesicles, that it can float on water. It forms when gas-rich, silica-rich magma is violently depressurized during an explosive eruption, freezing the expanding bubbles in place as volcanic glass. Its extremely low density and rough, abrasive texture have made it useful to people for thousands of years.
About Rhyolite
Rhyolite is a fine-grained volcanic igneous rock chemically equivalent to granite but formed by rapid cooling of silica-rich lava at or near Earth's surface rather than slow crystallization underground. Its high silica content makes rhyolitic magma extremely viscous, often producing explosive eruptions and distinctive flow-banded textures as the sticky lava moves sluggishly before solidifying. Rhyolite typically appears pale gray, pink, or tan and frequently contains visible bands or streaks recording its flow history.
Pumice vs Rhyolite FAQ
Is Pumice the same as Rhyolite?
No. Both are igneous rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 5–6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Pumice from Rhyolite?
Both sit near Mohs 5–6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Rhyolite feels noticeably heavier for its size (specific gravity 2.35–2.7 versus 0.25–0.9 for Pumice). Hold a thin edge to the light: Pumice is Opaque, translucent in thin shards, Rhyolite is Opaque.
Which is harder, Pumice or Rhyolite?
Rhyolite is harder: Mohs 5.5–7 against Mohs 5–6 for Pumice.
Which is more valuable, Pumice or Rhyolite?
Typical specimens of Pumice and Rhyolite trade in a similar range, around $10.
