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About EggletoniteHide

R. Anthony Eggleton
(Na,K,Ca)2(Mn,Fe)8(Si,Al)12O29(OH)7 · 11H2O
3 - 4
Crystal System:
Named by D. Peacor, P.J. Dunn, and W.B. Simmons in 1984 in honor of Dr. Richard Anthony Eggleton, mineralogist at the Australian National University and an expert on the crystal chemistry of the stilpnomelane group of minerals. It was first found in the Big Rock Quarry by Mr. Cecil Cosse in 1975 and submitted to the Smithsonian Institution for examination in 1977.
Ganophyllite Group. The sodium analogue of Ganophyllite.

Not to be confused with the unrelated mercury mineral Eglestonite.

Classification of EggletoniteHide

First published:

9 : SILICATES (Germanates)
E : Phyllosilicates
G : Double nets with 6-membered and larger rings
Dana 7th ed.:

74 : PHYLLOSILICATES Modulated Layers
1 : Modulated Layers with joined islands

16 : Silicates Containing Aluminum and other Metals
16 : Aluminosilicates of Mn

Physical Properties of EggletoniteHide

Light Brown
3 - 4 on Mohs scale

Optical Data of EggletoniteHide

Biaxial (-)
RI values:
nα = 1.566 nβ = 1.606 nγ = 1.606
Measured: 9°
Max Birefringence:
δ = 0.040
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
r > v strong

Chemical Properties of EggletoniteHide

(Na,K,Ca)2(Mn,Fe)8(Si,Al)12O29(OH)7 · 11H2O
IMA Formula:
(Na,K,Ca)xMn6(Si,Al)10O24(OH)4 · nH2O (x = 1-2; n = 7-11)
Common Impurities:

Crystallography of EggletoniteHide

Crystal System:
Cell Parameters:
a = 5.55 Å, b = 13.72 Å, c = 25 Å
β = 93.95°
a:b:c = 0.405 : 1 : 1.822
Unit Cell V:
1,899.13 ų (Calculated from Unit Cell)

Type Occurrence of EggletoniteHide

Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, 137143.
Peacor, D., Dunn, P.J., Simmons, W.B. (1984) Eggletonite, the Na analogue of ganophyllite. Mineralogical Magazine: 48: 93-96.

Synonyms of EggletoniteHide

Other Language Names for EggletoniteHide


Relationship of Eggletonite to other SpeciesHide

Other Members of this group:
Ganophyllite(K,Na,Ca)2Mn8(Si,Al)12(O,OH)32 · 8H2OMon.
Tamaite(Ca,K,Ba,Na)3-4Mn24(Si,Al)40(O,OH)112 · 21H2OMon.

Common AssociatesHide

Associated Minerals Based on Photo Data:
3 photos of Eggletonite associated with AegirineNaFe3+Si2O6
2 photos of Eggletonite associated with OrthoclaseK(AlSi3O8)
1 photo of Eggletonite associated with AlbiteNa(AlSi3O8)

Related Minerals - Nickel-Strunz GroupingHide

9.EG.05CymriteBaAl2Si2(O,OH)8 · H2OMon.
9.EG.10Naujakasite(Na,K)6(Fe2+,Mn2+,Ca)(Al,Fe)4Si8O26Mon. 2/m : B2/m
9.EG.15DmisteinbergiteCa(Al2Si2O8)Trig. 3 2 : P3 1 2
9.EG.20KampfiteBa12(Si11Al5)O31(CO3)8Cl5Mon. m
9.EG.25SträtlingiteCa2Al2SiO7 · 8H2OTrig.
9.EG.25VertumniteCa4Al4Si4O6(OH)24 · 3H2OMon. 2/m : P21/m
9.EG.30Ganophyllite(K,Na,Ca)2Mn8(Si,Al)12(O,OH)32 · 8H2OMon.
9.EG.30Tamaite(Ca,K,Ba,Na)3-4Mn24(Si,Al)40(O,OH)112 · 21H2OMon.
9.EG.35ZussmaniteK(Fe,Mg,Mn)13(Si,Al)18O42(OH)14Trig. 3 : R3
9.EG.40Franklinphilite(K,Na)4(Mn2+,Mg,Zn)48(Si,Al)72(O,OH)216 · 6H2OTric.
9.EG.40LennilenapeiteK6-7(Mg,Mn,Fe,Zn)48(Si,Al)72(O,OH)216 · 16H2OTric.
9.EG.40Parsettensite(K,Na,Ca)7.5(Mn,Mg)49Si72O168(OH)50 · nH2OMon. 2/m : B2/m
9.EG.40Stilpnomelane(K,Ca,Na)(Fe,Mg,Al)8(Si,Al)12(O,OH)36 · nH2OTric. 1 : P1
9.EG.45Tuscanite(K(Ca,Na)6(Si,Al)10O22[SO4,CO3,(OH)2] · H2OMon.
9.EG.55WickenburgiteCaPb3Al2Si10O24(OH)6Trig. 3m : P3 1c
9.EG.60HyttsjöitePb18Ba2Ca5Mn2+2Fe3+2Si30O90Cl · 6H2OTrig.
9.EG.65ArmbrusteriteK5Na7Mn15[(Si9O22)4](OH)10 · 4H2OMon. 2/m : B2/m
9.EG.70Britvinite[Pb7(OH)3F(BO3)2(CO3)][Mg4.5(OH)3(Si5O14)]Tric. 1 : P1
9.EG.75Bannisterite(Ca,K,Na)(Mn2+,Fe2+)10(Si,Al)16O38(OH)8 · nH2OMon. 2/m : B2/b

Related Minerals - Dana Grouping (8th Ed.)Hide,Na,Ca)2Mn8(Si,Al)12(O,OH)32 · 8H2OMon.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

16.16.1KanonaiteMn3+Al(SiO4)OOrth. mmm (2/m 2/m 2/m) : Pnnm
16.16.2SpessartineMn2+3Al2(SiO4)3Iso. m3m (4/m 3 2/m) : Ia3d
16.16.4SursassiteMn2+2Al3(SiO4)(Si2O7)(OH)3Mon. 2/m : P21/m
16.16.6KellyiteMn2+2Al(AlSiO5)(OH)4Hex. 6 : P63
16.16.9Ganophyllite(K,Na,Ca)2Mn8(Si,Al)12(O,OH)32 · 8H2OMon.
16.16.15Bannisterite(Ca,K,Na)(Mn2+,Fe2+)10(Si,Al)16O38(OH)8 · nH2OMon. 2/m : B2/b
16.16.17ZussmaniteK(Fe,Mg,Mn)13(Si,Al)18O42(OH)14Trig. 3 : R3
16.16.19HenritermieriteCa3Mn3+2(SiO4)2[◻(OH)4]Tet. 4/mmm (4/m 2/m 2/m) : I41/acd
16.16.22Piemontite{Ca2}{Al2Mn3+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for EggletoniteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Peacor, D., Dunn, P.J., Simmons, W.B. (1984) Eggletonite, the Na analogue of ganophyllite. Mineralogical Magazine: 48: 93-96.
Dunn, P.J., Gobel, V., Grice, J.D., Puziewicz, J., Shigley, J.E., Vanko, D.A., Zilczer, J. (1985) New mineral names. American Mineralogist: 70: 436-441.
Guggenheim, S. & Eggleton, R.A. (1986): Cation exchange in ganophyllite. Mineralogical Magazine 50, 517-520.
Hughes, J.M., Rakovan, J., Bracco, R., Gunter, M.E. (2003) The atomic arrangement of the ganophyllite-group modulated layer silicates as determined from the orthorhombic dimorph of tamaite, with the elusive 16.8 Å ganophyllite-group superstructure revealed. American Mineralogist: 88: 1324-1330.

Internet Links for EggletoniteHide

Localities for EggletoniteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
  • Liguria
    • Genoa
      • Ne
Bracco, R. (2012) Eggletonite e alleghanyite: due importanti novità dalla Val Graveglia. Prie, 7, 37-40.
  • Piedmont
    • Cuneo Province
      • Bellino
Piccoli, G.C., Vanini, F., Ciriotti, M.E., Marengo, A., Bittarello, E., Cámara, F., Kolitsch, U., Bracco, R., Balestra, C., Odicino, G., Brizio, P. (2020): Eggletonite e tamaite del Monte Maniglia, Bellino, Cuneo, Piemonte con aggiornamento sulla mineralogia locale. Micro, 18, 60-66.
  • Tokyo Metropolis
    • Nishitama district
      • Okutama-cho
Matsubara S, Miyawaki R, Tiba T, Imai H (2000) Tamaite, the Ca-analogue of ganophyllite, from the Shiromaru mine, Okutama, Tokyo, Japan. Journal of Mineralogical and Petrological Sciences 95, 79-83; MinRec 32:419. ; Tanaka, T. & Hamane, D. (2016) Epidote-(Sr) from Shiromaru mine, Tokyo prefecture, Japan. (conference presentation R1-P14)
  • Arkansas
    • Pulaski Co.
      • Little Rock
Rocks and Minerals, (1988) 63:104-125; Rocks and Minerals, (1989) 64:314-322
Peacor, D., Dunn, P. J. & Simmons, W. B. (1984): Eggletonite, the Na analogue of ganophyllite. Mineralogical Magazine. 48, 93-96.; Min News (1991) 7:5 pp 4,5
Mineral and/or Locality  
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