Pumice
Pumice is igneous (volcanic, vesicular glass). In the hand, it rates 5 to 6 (glass walls; crumbles easily) on the Mohs scale, and it runs pale gray and cream. Rock foam: pale, full of tiny bubbles, rough as sandpaper, and it floats on water. Explosive volcanic eruptions worldwide; notable: Italy (Lipari), Greece (Santorini), USA, Indonesia.
The geology.
Pumice carries the formula . It belongs to the, system. On paper it is igneous (volcanic, vesicular glass).
It sits at 5 to 6 (glass walls; crumbles easily) on the Mohs scale. The surface reads dull. Light behaviour is opaque. Specific gravity runs 0.25 to 1.0 (floats). The streak is,. It breaks with crumbly, vesicular.
Rock foam: pale, full of tiny bubbles, rough as sandpaper, and it floats on water.
Expect to see it as raw foam-rock pieces, abrasive blocks or beach drift.
The origins.
Explosive volcanic eruptions worldwide; notable: Italy (Lipari), Greece (Santorini), USA, Indonesia.
On value, the database notes: common and very affordable.
Traditional associations.
In energy work traditions, associated with releasing what weighs you down.
Recorded here because it is part of how this material is sold, not because it is a property of the material.
Spotting the real thing.
Rock foam: pale, full of tiny bubbles, rough as sandpaper, and it floats on water.
| Looks like | How to tell them apart |
|---|---|
| Scoria | Scoria is darker, denser, with bigger holes, it sinks |
| Coral skeleton | Coral shows organized polyp patterns; pumice bubbles are random |
| Industrial foam/concrete | Man-made foams feel plasticky or cement-gritty |
At-home tests.
None of these need a lab. A 10x loupe, good daylight and a steady hand cover most of what a buyer needs to know about pumice.
| Test | What you should see |
|---|---|
| Float test | genuine pumice floats (at least initially) |
| By weight | Ultra-lightweight |
| By eye | Abrasive feel |
Anything that scratches, burns or dissolves the piece is a lab job. Get it appraised rather than testing it apart.
Care & handling.
At 5 to 6 (glass walls; crumbles easily) on the Mohs scale it handles careful wear but scratches against quartz and dust. Store it separately and take rings off before rough work.
It breaks with crumbly, vesicular, which is worth knowing before you set it or drop it.
Warm water and a soft cloth clean almost everything. Ultrasonic tanks, steamers and household cleaners are where pieces get ruined.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is . Crystal system:,. Specific gravity: 0.25 to 1.0 (floats). Streak:,. Cleavage and fracture: Crumbly, vesicular.
How it reaches the market
Explosive volcanic eruptions worldwide; notable: Italy (Lipari), Greece (Santorini), USA, Indonesia.
What it gets confused with
Scoria: Scoria is darker, denser, with bigger holes, it sinks. Coral skeleton: Coral shows organized polyp patterns; pumice bubbles are random. Industrial foam/concrete: Man-made foams feel plasticky or cement-gritty.
What it is worth
Common and very affordable.
One more thing
After big eruptions, pumice rafts the size of cities drift across oceans, rock literally sailing the sea.
An education-first guide.
No product links here. We do not sell pumice, and a guide that only covers our own shelves would not be much of a guide.
Explore the Crystal Guide