Eastonite

Where it forms, where it's found

Type locality: Sherrer Quarry
C.K. Williams Quarry complex
Chestnut Hill
Easton
Northampton County
Pennsylvania
USA
40.7134°, -75.1966°

20recorded occurrences

Source · OpenStreetMap

Crystallography

Crystal system: Monoclinic
Comment: No crystallography

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
45.84%
13AlAluminium Aluminium 3 26.982 80.946
19.33%
14SiSilicon Silicon 2 28.085 56.170
13.41%
12MgMagnesium Magnesium 2 24.305 48.610
11.61%
19KPotassium Potassium 1 39.098 39.098
9.33%
1HHydrogen Hydrogen 2 1.008 2.016
0.48%
Total 418.828 100.00%
Mass share = atoms × atomic mass ÷ molar mass × 100
From IMA formula

Mass composition breakdown
Element	Atoms	At. mass g/mol	Mass g/mol	Mass share
8OOxygen	Oxygen	12	15.999	191.988	45.84%
13AlAluminium	Aluminium	3	26.982	80.946	19.33%
14SiSilicon	Silicon	2	28.085	56.170	13.41%
12MgMagnesium	Magnesium	2	24.305	48.610	11.61%
19KPotassium	Potassium	1	39.098	39.098	9.33%
1HHydrogen	Hydrogen	2	1.008	2.016	0.48%
	Total	418.828	100.00%

Synonyms

Eastoniet

In other languages

German: Eastonit
Italian: Eastonite

Classification

Strunz

10th ed.

9.EC.20

9SilicatesClass
9.EPhyllosilicatesDivision
9.ECPhyllosilicates with mica sheets, composed of tetrahedral and octahedral netsGroup
9.EC.20EastoniteSpecies

Group, growth & confusion

9 members

Literature, links & citation

Citations

1899Hamilton, Samuel Harbert (1899) Mineral Collector, 6, 118.
1925Winchell, A.N. (1925) Studies in the mica group - Part 1. American Journal of Science, 9, 309-327.
1987Livi, Kenneth J. T., Veblen, David R. (1987) Eastonite from Easton, Pennsylvania: A mixture of phlogopite and a new form of serpentine. American Mineralogist, 72 (1-2) 113-125
1998Rieder, M., Cavazzini, G., D’Yakonov, Y.S., Frank-Kamenetskii, V.A., Gottardt, G., Guggenheim, S., Koval, P.V., Muller, G., Neiva, A.M.R., Radoslovich, E.W., Robert, J.L., Sassi, F.P., Takeda, H., Weiss, Z., Wones, D.R. (1998) Nomenclature of the micas. The Canadian Mineralogist, 36 (3) 905-912

Cite this entry

@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Eastonite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/eastonite-6909},
  note      = {Accessed 2026-05-11}
}