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.

Wikimedia Commons has media related to Rhyodacite.


This article is issued from Wikipedia - version of the Friday, September 04, 2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.