Ian Crawford

Andesite Andesite Type of volcanic rock For the extinct cephalopod genus, see Andesites. Andesite (/ˈændəzaɪt/)[1] is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.[2] Quick facts Composition, Primary ... Andesite Igneous rock A sample of andesite (dark groundmass) with amygdaloidal vesicles filled with zeolite. Diameter of view is 8 cm. Composition Primary Intermediate: plagioclase (often andesine) and pyroxene or hornblende Secondary Magnetites, biotite, sphene, and quartz Close Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs.…

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