Phengite

Where it forms, where it's found

463recorded occurrences

Source · OpenStreetMap

Varieties

MaripositeK(Al,Cr)₂(Al,Si)₄O₁₀(OH)₂
Variety
—

Chemical composition

Constituent elements: Mass composition breakdown
Element Atoms At. mass g/mol Mass g/mol Mass share
8OOxygen Oxygen 12 15.999 191.988
45.13%
14SiSilicon Silicon 3.5 28.085 98.297
23.11%
13AlAluminium Aluminium 2 26.982 53.964
12.68%
19KPotassium Potassium 1 39.098 39.098
9.19%
26FeIron Iron 0.5 55.845 27.922
6.56%
12MgMagnesium Magnesium 0.5 24.305 12.152
2.86%
1HHydrogen Hydrogen 2 1.008 2.016
0.47%
Total 425.439 100.00%
Mass share = atoms × atomic mass ÷ molar mass × 100
From Mindat formula

Mass composition breakdown
Element	Atoms	At. mass g/mol	Mass g/mol	Mass share
8OOxygen	Oxygen	12	15.999	191.988	45.13%
14SiSilicon	Silicon	3.5	28.085	98.297	23.11%
13AlAluminium	Aluminium	2	26.982	53.964	12.68%
19KPotassium	Potassium	1	39.098	39.098	9.19%
26FeIron	Iron	0.5	55.845	27.922	6.56%
12MgMagnesium	Magnesium	0.5	24.305	12.152	2.86%
1HHydrogen	Hydrogen	2	1.008	2.016	0.47%
	Total	425.439	100.00%

Synonyms

Fengite
Phengit

Literature, links & citation

Citations

1853von Kobell, Franz (1853) Tafeln zur Bestimmung der Mineralien mittelst einfacher chemischer Versuche auf trockenem und nassem Wege [Tables for the determination of minerals by means of simple dry and wet chemical experiments] (5th ed.). J. Lindauer'sche Buchhandlung.
1879Tschermak, G. (1879) Die Glimmergruppe (II. Theil). Zeitschrift für Kristallographie, 3 (1). 122-167 doi:10.1524/zkri.1879.3.1.122DOI: 10.1524/zkri.1879.3.1.122
1925Winchell, A. N. (1925) Studies in the mica group (abstract) American Mineralogist, 10 (3) 52-53
1964Crowley, M. S., Roy, Rustum (1964) Crystalline solubility in the muscovite and phlogopite groups. American Mineralogist, 49 (3-4) 348-362
1965Exner, C. (1965): Phengit in Gesteinen der östlichen Hohen Tauern. Carinthia II, 155./75., 70-80. [http://www.zobodat.at/pdf/CAR_155_75_0080-0089.pdf; with info on the history of the mineral name]

Cite this entry

@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Phengite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/phengite-3189},
  note      = {Accessed 2026-05-11}
}