Meta-Rhyolith

Meta-rhyolite is a variant of the rock rhyolite. Rhyolite is a felsic volcanic rock with a chemical and mineralogical composition similar to that of granite. It has the highest silica content among felsic volcanic rocks and is approximately 65% to 75% silicon dioxide (SiO2). The term "meta-rhyolite" indicates that it is a metamorphic variant of rhyolite. In the following I will go into more detail about the properties and formation of rhyolite.

Rhyolite is usually light colored, with shades of grey, light green or light red predominating. It consists mainly of quartz and feldspar. Quartz grades vary between 20% and 60%, with grades greater than 50% likely due to subsequent enrichment of quartz in the rock. The remainder of the rock is mainly feldspar, with plagioclase accounting for 10% to 65% and alkali feldspar (sanidine and/or orthoclase) accounting for 35% to 90% of the feldspar content in true rhyolite. Rhyolite also contains small amounts (typically no more than 2% and a maximum of 15%) of mafic minerals such as biotite, hornblende or augite. Rhyodazite can contain up to 20% of such components. In addition, rhyolite contains traces of minerals such as magnetite, hematite, cordierite, garnet or olivine.

Rhyolite typically has a porphyry texture. This means that it consists of a dense, fine-grained matrix in which individual crystals called phenocrystals are only visible under a microscope. Composed mainly of quartz and feldspar, these phenocrystals range in size from a few millimeters to several centimeters. However, there are also rhyolites without phenocrystals that are entirely fine-grained and are referred to as aphyric or felsic rhyolites. Some rhyolite rocks also show clear flow structures. Solidification of a rhyolitic magma mass can result in a regular columnar fissure pattern showing hexagonal columns similar to those found in basalt[1External link].