Phengite Explained
| Phengite |
| Category: | Mica group |
| Formula: | K(AlMg)2(OH)2(SiAl)4O10 |
Phengite is a series name for dioctahedral micas of composition K(Al,Mg)2(OH)2(Si,Al)4O10. It is common for Mg or Fe2+ to substitute for Al on the Y site and a corresponding increase in Si on the Z site in the mica group formula X2Y4–6Z8O20(OH, F)4. Similar to muscovite but with addition of magnesium. It is a non-IMA recognized mineral name representing the series between muscovite and celadonite.[1] [2]
The silica content of phengite has been proposed as a geobarometer for the metamorphism of low grade schists.[3]
References
- Glossary of Geology, Fifth Edition, Eds. K.K.E. Neiendorf, J.P. Mehl, J.A. Jackson, American Geological Institute, 2005
- von Kobell, Franz (1853) Tafeln zur Bestimmung des Mineralien, 5th edition, Munchen.
- Guidotti, Charles V. (1984) Micas in metamorphic Rocks, reviews in Mineralogy, 13: 357-467.
- Rieder et al. (1998): Nomenclature of the micas. Canadian Mineralogist 36: 905-912.
- Mookherjee, M., and Redfern, S.A.T. (2002) A high-pressure Fourier-transform infrared study of the interlayer and Si-O stretching region in phengite-2M 1. Clay Minerals: 37: 323-336.
- Cibin, G., G. Cinque, A. Marcelli, A. Mottana, & R. Sassi (2008): The octahedral sheet of metamorphic 2M1-phengites: a combined EMPA and AXANES study: American Mineralogist 93, 414-425.
Notes and References
- http://www.mindat.org/min-3189.html Mindat.org
- https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Phengit Mineralienatlas: Phengit
- M. E. Fleet and R. A. Howie, Rock-Forming Minerals, Vol. 3A: Micas, Geological Society of London; 2nd ed, 2006, p. 132, (accessed through Google books)
