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Andesite identification and geology

An intermediate volcanic extrusive igneous rock with a silica content of approximately 57–63% by weight, typically gray to dark gray with a fine-grained or porphyritic texture. Andesite is the extrusive equivalent of diorite and is the dominant rock type at convergent plate boundaries, particularly in continental volcanic arcs. It is named after the Andes Mountains, where it is extremely abundant. Field: petrology. Example: Mount Pinatubo in the Philippines erupted andesitic to dacitic magma in 1991, producing one of the largest eruptions of the 20th century.. Related terms: Diorite, Dacite, Volcanic arc, Porphyritic.

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:41.970235+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Andesite mean in geology?
An intermediate volcanic extrusive igneous rock with a silica content of approximately 57–63% by weight, typically gray to dark gray with a fine-grained or porphyritic texture. Andesite is the extrusive equivalent of diorite and is the dominant rock type at convergent plate boundaries, particularly in continental volcanic arcs. It is named after the Andes Mountains, where it is extremely abundant.
What is an example of Andesite?
Mount Pinatubo in the Philippines erupted andesitic to dacitic magma in 1991, producing one of the largest eruptions of the 20th century.
Which earth-science field uses the term Andesite?
Andesite is used in petrology.
Which terms are related to Andesite?
Related terms in this reference are Diorite, Dacite, Volcanic arc, Porphyritic.

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