igneous
Pumice
Pumice (Volcanic Glass with Vesicular Texture)
Hardness: 5-6 on Mohs scale (brittle, breaks easily). Color: Light gray, tan, cream, or yellowish-white, often with iron staining. Luster: Dull to earthy. Texture: Highly vesicular, porous, lightweight (often floats on water).…
- Hardness
- 5-6 on Mohs scale (brittle, breaks easily)
- Luster
- Dull to earthy
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Physical properties
Hardness: 5-6 on Mohs scale (brittle, breaks easily). Color: Light gray, tan, cream, or yellowish-white, often with iron staining. Luster: Dull to earthy. Texture: Highly vesicular, porous, lightweight (often floats on water). Mineral composition: Primarily amorphous silica-rich volcanic glass, with trace feldspar and quartz.
Formation & geological history
Formed during explosive volcanic eruptions when highly gas-charged, felsic (silica-rich) magma cools extremely rapidly, trapping gas bubbles as vesicles within the solidified lava.
Uses & applications
Widely used as an abrasive in polishing products, soap, and cosmetic foot scrubs (pumice stones), as a lightweight aggregate in concrete, in stonewashing denim, and as a soil conditioner in horticulture.
Geological facts
Pumice is so light and full of air pockets (vesicles) that many fresh specimens can float on water until they eventually become waterlogged.
Field identification & locations
Identified in the field by its sponge-like vesicular texture, extreme light weight, and rough abrasive surface. Commonly found near active or ancient explosive volcanic regions, such as the Mediterranean, Pacific Northwest US, and New Zealand.
