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Felsite covered with dendritic pyrolusite Dike of felsite on Islay in Scotland. Felsite is a very fine-grained volcanic rock that may or may not contain larger crystals.Felsite is a field term for a light-colored rock that typically requires petrographic examination or chemical analysis for more precise definition.
Rocks with greater than 90% felsic minerals can also be called leucocratic, [4] from the Greek words for white and dominance. Felsite is a petrologic field term used to refer to very fine-grained or aphanitic, light-colored volcanic rocks which might be later reclassified after a more detailed microscopic or chemical analysis.
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Epidosite – Hydrothermally altered epidote- and quartz-bearing rock; Felsite – Very fine-grained volcanic rock that sometimes contains larger crystals; Flint – Cryptocrystalline form of the mineral quartz; Ganister – Hard, fine-grained quartzose sandstone, or orthoquartzite; Gossan – Intensely oxidized, weathered or decomposed rock
Felsic eruption forms felsic volcanic rocks near the volcano and a spectrum of volcano-sedimentary sequence in the sea in Archean. [1] Archean felsic volcanic rocks are felsic volcanic rocks that were formed in the Archean Eon (4 to 2.5 billion years ago). [2] The term "felsic" means that the rocks have silica content of 62–78%. [3]
Quartzolite or silexite is an intrusive igneous rock, in which the mineral quartz is more than 90% of the rock's felsic mineral content, with feldspar at up to 10%. [ 1 ] : 135 [ 2 ] Typically, quartz forms more than 60% of the rock, [ 3 ] the rest being mostly feldspar although minor amounts of mica or amphibole may also be present. [ 2 ]
Quartz monzonite is an intrusive, felsic, igneous rock that has an approximately equal proportion of orthoclase and plagioclase feldspars. It is typically a light colored phaneritic (coarse-grained) to porphyritic granitic rock. The plagioclase is typically intermediate to sodic in composition, andesine to oligoclase.
Cerro Mackay, a mountain in Coyhaique in Chile, made of columns of adakite [1] Closer view of the adakite columns of Cerro Mackay, Chile. Adakites are volcanic rocks of intermediate to felsic composition that have geochemical characteristics of magma originally thought to have formed by partial melting of altered basalt that is subducted below volcanic arcs. [2]