Andesite is primarily divided into three main subtypes based on their mineral composition: quartz-bearing andesites (often referred to as dacites), hornblende- and biotite-andesites, and pyroxene-andesites.
Major Subdivisions of Andesite
The classification of andesite, a common volcanic rock formed from solidified lava, involves recognizing key variations in its mineral content. According to Britannica, there are three distinct subdivisions within this rock family, each characterized by specific mineral assemblages.
Here are the main subtypes of andesite:
| Andesite Subtype | Key Characteristics |
|---|---|
| Quartz-bearing Andesites (Dacites) | These andesites contain significant amounts of quartz. They are sometimes considered a separate rock family altogether due to their distinct compositional differences. |
| Hornblende- and Biotite-Andesites | This subtype is characterized by the prominent presence of hornblende and biotite, which are common ferromagnesian minerals. |
| Pyroxene-Andesites | Distinguished by the dominance of pyroxene minerals, this type of andesite reflects specific conditions during its formation. |
These classifications highlight the varied mineralogical compositions that define different types of andesite, influenced by their magmatic origins and cooling processes. For further details on andesite and its characteristics, you can refer to the Britannica article on Andesite.
