Rhyodacite

A sample of rhyodacite from Slovakia

Rhyodacite is an extrusive volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of granodiorite. Phenocrysts of sodium-rich plagioclase, sanidine, quartz, and biotite or hornblende are typically set in an aphanitic to glassy light to intermediate-colored matrix.
Rhyodacite is a high silica rock containing 20% to 60% quartz with the remaining constituents being mostly feldspar. The feldspar is a mix of alkaline feldspar and plagioclase, with plagioclase forming 35% to 65% of the mix.^[1] Rhyodacite often exists as explosive pyroclastic volcanic deposits.

References

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Volcanoes
Volcano types	Caldera Cinder cone Complex volcano Cryovolcano Fissure vent Lava cone Lava dome Maar Mud volcano Parasitic cone Pyroclastic cone Pyroclastic shield Rootless cone Shield volcano Somma volcano Stratovolcano Subglacial volcano Submarine volcano Supervolcano Volcanic cone Volcanic field (polygenetic · monogenetic)
Volcanic rocks	Volcanic rock Agglomerate Andesite Basalt Basaltic andesite Benmoreite Blairmorite Dacite Felsite Komatiite Latite Leucitite Nephelinite Obsidian Phonolite Phonotephrite Rhyodacite Rhyolite Tephriphonolite Trachyte Trachyandesite Trachybasalt Tuff
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