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Dacite

A light gray volcanic rock between andesite and rhyolite, typical of explosive lava domes.

Dacite specimen
Photo: ScoriaPumice, CC0, via Wikimedia Commons

How to identify dacite

  • Light to medium gray.
  • Scattered white feldspar and dark hornblende crystals.
  • Fine-grained base; may contain small quartz grains.

Often confused with

Where it's found

  • Mount St. Helens, Washington
  • Lassen Peak, California
  • Mount Pinatubo, Philippines

Uses

Aggregate and building stone.

Rock tumbling

Can be tumbled with care.

Did you know?

The lava dome growing inside Mount St. Helens after 1980 is dacite.

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