Eggletonite Mineral Data

Eggletonite Mineral Data +

General Eggletonite Information

Chemical Formula:

Na2Mn8[Si11AlO29](OH)7·11(H2O)

Composition:

Molecular Weight = 1,602.61 gm

Sodium 2.87 % Na 3.87 % Na₂O

Manganese 27.42 % Mn 35.41 % MnO

Aluminum 1.68 % Al 3.18 % Al₂O₃

Silicon 19.28 % Si 41.24 % SiO₂

Hydrogen 1.82 % H 16.30 % H₂O

Oxygen 46.92 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Na₂Mn²⁺₈Si₁₁AlO₂₉(OH)₇·11(H₂O)

Environment:

Miarolitic cavities in nepheline syenite. Probably isostructural with ganophyllite.

IMA Status:

Approved IMA 1984

Locality:

Big Rock Quarry, Little Rock, Pulaski County, Arkansas, USA. Link to MinDat.org Location Data.

Name Origin:

Named for R. A. Eggleton, Australian National University.

Eggletonite Image

Images:

Eggletonite

Comments: Brown micro crystals of eggletonite in syenite.
Location: 3M Quarry, Little Rock, Pulaski County, Arkansas, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Eggletonite Crystallography

Axial Ratios:

a:b:c =0.4048:1:1.8221

Cell Dimensions:

a = 5.554, b = 13.72, c = 25, Z = 2; beta = 93.95° V = 1,900.50 Den(Calc)= 2.80

Crystal System:

MonoclinicSpace Group: Ia or I2/a

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.694(1), 12(1), 2.598(0.55),

Physical Properties of Eggletonite

Cleavage:

[001] Perfect

Color:

Golden brown.

Density:

2.76

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Habit:

Acicular - Occurs as needle-like crystals.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Habit:

Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)

Hardness:

3-4 - Calcite-Fluorite

Luster:

Vitreous (Glassy)

Streak:

light brown

Optical Properties of Eggletonite

Gladstone-Dale:

CI meas= 0.045 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.059 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2117,KPDmeas= 0.2147,KC= 0.2249

Optical Data:

Biaxial (-), a=1.566, b=1.606, g=1.606, bire=0.0400, 2V(Calc)=0, 2V(Meas)=9.

Calculated Properties of Eggletonite

Electron Density:

r_electron=2.73 gm/cc
note: r_Eggletonite=2.76 gm/cc.

Fermion Index

Fermion Index = 0.00923
Boson Index = 0.99077

Photoelectric:

PE_Eggletonite= 7.73 barns/electron
U=PE_Eggletonite x r_electron= 21.13 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Eggletonite is Not Radioactive

Eggletonite Classification

Dana Class:

74.1.2.2 (74)Phyllosilicate Modulated Layers

(74.1)with joined islands

(74.1.2)Ganophyllite group

74.1.2.1 Ganophyllite (K,Na)2(Mn,Al,Mg)8(Si,Al)12O29(OH)7·8-9(H2O) A2/a 2/m

74.1.2.2 Eggletonite Na2Mn8[Si11AlO29](OH)7·11(H2O) Ia or I2/a Mono

74.1.2.3 Tamaite! (Ca,K,Ba,Na)3-4Mn24(Si,Al)40(O,OH)112·21(H2O) P 2₁/a 2/m

Strunz Class:

VIII/H.17-70 VIII - Silicates

VIII/H - Phyllosilicates (layered) Mica like layered silicates with [Si4O10]4- and related groups

VIII/H.17 - Stilpnomelane series

VIII/H.17-10 Bannisterite KCa(Mn,Fe,Zn,Mg)21(Si,Al)32O76(OH)16·4-12(H2O) A2/a 2/m

VIII/H.17-20 Bariumbannisterite* (K,H3O)(Ba,Ca)(Mn,Fe,Mg)21(Si,Al)32O80(O,OH)16·4-12(H2O) Mono

VIII/H.17-30 Lennilenapeite K6-7(Mg,Mn,Fe,Fe,Zn)48(Si,Al)72(O,OH)216·16(H2O) Unk (pseudo-HEX) Tri

VIII/H.17-40 Stilpnomelane K(Fe,Mg,Fe)8(Si,Al)12(O,OH)27·n(H2O) P1 1

VIII/H.17-45 Franklinphilite (K,Na)4(Mn,Mg,Zn)48(Si,Al)72(O,OH)216·6(H2O) pseudo-HEX P1 or P1 Tri

VIII/H.17-50 Parsettensite (K,Na,Ca)(Mn,Al)7Si8O20(OH)8·2(H2O)(?) C 2/m 2/m

VIII/H.17-60 Ganophyllite (K,Na)2(Mn,Al,Mg)8(Si,Al)12O29(OH)7·8-9(H2O) A2/a 2/m

VIII/H.17-70 Eggletonite Na2Mn8[Si11AlO29](OH)7·11(H2O) Ia or I2/a Mono

VIII/H.17-75 Tamaite! (Ca,K,Ba,Na)3-4Mn24(Si,Al)40(O,OH)112·21(H2O) P 2₁/a 2/m

VIII/H.17-80 Ekmanite? (Fe,Mg,Mn,Fe)3(Si,Al)4O10(OH)2·2(H2O) Unk Ortho

Other Eggletonite Information

References:

NAME( Dana8) PHYS. PROP.(Dana8) OPTIC PROP.(Dana8)

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Print or Cut-and-Paste your Eggletonite Specimen Label here :

Eggletonite

Na2Mn8[Si11AlO29](OH)7·11(H2O)
Dana No: 74.1.2.2 Strunz No: VIII/H.17-70
Locality:

Notes: