igneous
Andesite
Andesite
Hardness: 6-7 (Mohs scale); Color: gray, greenish-gray, or brownish; Luster: dull to earthy; Texture: aphanitic to porphyritic with small visible phenocrysts; Specific Gravity: 2.4-2.8
- Hardness
- 6-7 (Mohs scale)
- Color
- gray, greenish-gray, or brownish
- Luster
- dull to earthy
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs scale); Color: gray, greenish-gray, or brownish; Luster: dull to earthy; Texture: aphanitic to porphyritic with small visible phenocrysts; Specific Gravity: 2.4-2.8
Formation & geological history
Formed through the rapid cooling of intermediate-composition lava at or near the Earth's surface, typically at volcanic arcs above subduction zones.
Uses & applications
Used primarily as crushed stone for road construction, railroad ballast, and high-quality aggregate in concrete due to its durability and resistance to slip.
Geological facts
Andesite is the second most common volcanic rock in the Earth's crust after basalt and is named after the Andes Mountains where it is found in abundance.
Field identification & locations
Identify by its intermediate gray-green color and salt-and-pepper appearance caused by plagioclase feldspar and hornblende/pyroxene. It is less dark than basalt and lacks the high quartz content of rhyolite.
