Felsiteis a very fine-grainedvolcanic rockthat may or may not contain largercrystals.Felsite is a field term for a light-colored rock that typically requirespetrographicexamination or chemical analysis for more precise definition. Color is generally white through light gray, or red to tan and may include any color except dark gray, green or black (the colors oftrap rock).[1]The mass of the rock consists of a fine-grainedmatrixoffelsicmaterials, particularlyquartz,sodiumandpotassium feldspar,[2]and may be termed a quartz felsite or quartz porphyry if the quartz phenocrysts are present. This rock is typically ofextrusiveorigin, formed by compaction of fine volcanic ash, and may be found in association withobsidianandrhyolite.In some cases, it is sufficiently fine-grained for use in makingstone tools.Its fine texture and felsic components allow for good knapped pieces, much like workingchert,producingconchoidal fracture.
Dendriticmanganese oxides such aspyrolusiteand/or iron oxides such aslimonitemay precipitate along rock crevices, giving some rock chunk surfaces multicolored or arborescent patterned textures.
References
edit- ^Klein, Cornelis and Hurlbut, Cornelius S. (1986),Manual of Mineralogy,Wiley, p. 484ISBN0-471-80580-7
- ^McDonnell, S.; Troll, V. R.; Emeleus, C. H.; Meighan, I. G.; Brock, D.; Gould, R. J. (October 2004)."Intrusive history of the Slieve Gullion ring dyke, Ireland: implications for the internal structure of silicic sub-caldera magma chambers".Mineralogical Magazine.68(5): 725–738.Bibcode:2004MinM...68..725M.doi:10.1180/0026461046850215.ISSN0026-461X.S2CID140159457.
 | This article aboutigneous petrologyis astub.You can help Wikipedia byexpanding it. |