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rhyolite

rhyolite

SRI Petrography ID: 22

red coloured, typical rhyolite, fine grained matrix, containing visible mineral phases (porphyritic texture: crystals in fine grained matrix): colourless: quartz, white: feldspar, black: biotite

Names

[de] Rhyolit
[en] rhyolite

Description

Rhyolite is a fine grained, volcanic rock (tuffs, rarely lavas), in composition equal to the plutonic equivalent granite. Rhyolite is formed from silica-rich magma and contains often glassy or microcrystalline aggregates.
Main mineral composition: quartz, feldspar and accessory minerals like biotite and hornblende

Color

very light-coloured

Grain Size

fine grained, sometimes porphyric

Texture

aphanitic to porphyric, usually showing flow-lines (fluidal textures).

Minerals

quartz, feldspar and accessory minerals like biotite and hornblende

Occurences

rhyolite is known all over the world in continental crust, island arcs and dykes.

Comments

Rhyolite is the volcanic equivalent to granite

Classification

Class

IGNEOUS ROCKS

Broader Terms

fine-grained crystalline rocks