Epistolite Mineral Data

Epistolite Mineral Data +

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General Epistolite Information

Chemical Formula:

Na4Nb2Ti(Si2O7)2O2(OH)2·4(H2O)

Composition:

Molecular Weight = 758.20 gm

Sodium 11.49 % Na 15.49 % Na₂O

Calcium 1.43 % Ca 2.00 % CaO

Titanium 0.25 % Ti 0.42 % TiO₂

Manganese 0.29 % Mn 0.37 % MnO

Niobium 23.53 % Nb 33.66 % Nb₂O₅

Iron 0.29 % Fe 0.42 % Fe₂O₃

Silicon 14.82 % Si 31.70 % SiO₂

Hydrogen 1.25 % H 11.21 % H₂O

Oxygen 45.24 % O

Fluorine 1.40 % F 1.40 % F

- % F -0.59 % -O=F₂

______ ______

100.00 % 96.09 % = TOTAL OXIDE

Empirical Formula:

Na_3.79Ca_0.27Mn²⁺_0.04Nb_1.92Ti_0.04Fe³⁺_0.04(Si₂O₇)₂O₂(OH)_1.44F_0.56·4(H₂O)

IMA Status:

Valid Species (Pre-IMA) 1897

Locality:

Tugtupagtakorfia, Kvanefield, and Taseq slope, Ilimaussag intrusion, Julianehaab area, southern Greenland. Link to MinDat.org Location Data.

Name Origin:

Named for the Greek for "letter" in allusion to the flat, rectangular form and white color.

Epistolite Image

Images:

Epistolite

Comments: Plate-like crystals of pearly white epistolite to 2.7 cm.
Location: Ilimaussaq, Kvanefjeld, Greenland. Scale: 3.5 cm.
© John Veevaert

Epistolite Crystallography

Axial Ratios:

a:b:c =0.7615:1:1.6793

Cell Dimensions:

a = 5.46, b = 7.17, c = 12.041, Z = 1; alpha = 103.63°, beta = 96.01°, gamma = 89.98° V = 455.59 Den(Calc)= 2.76

Crystal System:

Triclinic - PinacoidalH-M Symbol ( 1) Space Group: P1

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

By Intensity(I/I_o): 4.33(1), 6.11(1), 2.72(0.8),

Crystal Structure:

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Sokolova E V , Hawthorne F C , The Canadian Mineralogist , 42 (2004) p.797-806, The crystal chemistry of epistolite

Physical Properties of Epistolite

Cleavage:

[001] Perfect, [110] Distinct

Color:

White, Yellowish white, Gray, Light brown.

Density:

2.65 - 2.89, Average = 2.77

Diaphaniety:

Translucent

Fracture:

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

Habit:

Platy - Sheet forms (e.g. micas).

Hardness:

1-1.5 - Talc or a little harder

Luster:

Pearly

Streak:

white

Optical Properties of Epistolite

Gladstone-Dale:

CI meas= -0.006 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.01 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2345,KPDmeas= 0.2337,KC= 0.2323

Optical Data:

Biaxial (-), a=1.61, b=1.65, g=1.682, bire=0.0720, 2V(Calc)=80, 2V(Meas)=60.

Calculated Properties of Epistolite

Electron Density:

r_electron=2.71 gm/cc
note: r_Epistolite=2.77 gm/cc.

Fermion Index

Fermion Index = 0.00754
Boson Index = 0.99246

Photoelectric:

PE_Epistolite= 35.22 barns/electron
U=PE_Epistolite x r_electron= 95.39 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Epistolite is Not Radioactive

Epistolite Classification

Dana Class:

56.2.7.1 (56)Sorosilicate Si2O7 Groups and O, OH, F. and H2O

(56.2)with cations in [4] and/or >[4] coordination

(56.2.7)Murmanite group

56.2.7.1 Epistolite Na4Nb2Ti(Si2O7)2O2(OH)2·4(H2O) P1 1

56.2.7.2 Murmanite Na3(Ti,Nb)4(Si2O7)2O4·4(H2O) P1 ? 1

56.2.7.3 Shkatulkalite! Na10MnTi3Nb3(Si2O7)6(OH)2F·12(H2O) P 2,Pm,P 2/m Mono

Strunz Class:

VIII/C.14-50 VIII - Silicates

VIII/C - Sorosilicates with [Si2O7]6-, with anions unfamiliar to tetraheders [O,OH,F]

VIII/C.14 - Fresnoite - Belkovite series

VIII/C.14-20 Muirite Ba10Ca2MnTiSi10O30(OH,Cl,F)10 P 4/mmm 4/m 2/m 2/m

VIII/C.14-30 Belkovite! Ba3(Nb,Ti)6(Si2O7)2O12 P 62m 6 m2

VIII/C.14-40 Murmanite Na3(Ti,Nb)4(Si2O7)2O4·4(H2O) P1 ? 1

VIII/C.14-50 Epistolite Na4Nb2Ti(Si2O7)2O2(OH)2·4(H2O) P1 1

VIII/C.14-70 Lomonosovite Na5Ti2O2(Si2O7)(PO4) P1 1

VIII/C.14-80 Vuonnemite Na11Nb2TiSi4O12(PO4)2O5F2 P1 1

VIII/C.14-110 Bussenite! Na2(Ba,Sr)2(Fe,Mn)TiSi2O7(CO3)(OH)3F P1 1

VIII/C.14-120* Quadruphite-VII Na14CaMgTi4[Si2O7]2(PO4)4O4F2 P1 1

VIII/C.14-120 Quadruphite-VIII Na14CaMgTi4(Si2O7)2(PO4)4O4F2 P1 1

VIII/C.14-130 Sobolevite Na11(Na,Ca)4(Mg,Mn)Ti4(Si4O12)(PO4)4O5F3 P1 1

VIII/C.14-140* Polyphite-VII Na17Ca3Mg(Ti,Mn)4[Si2O7]2(PO4)6O2F6 P1 1

VIII/C.14-140 Polyphite-VIII Na17Ca3Mg(Ti,Mn)4[Si2O7]2(PO4)6O2F6 P1 1

Other Epistolite Information

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990, CanMin, 42:797) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

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Epistolite

Na4Nb2Ti(Si2O7)2O2(OH)2·4(H2O)
Dana No: 56.2.7.1 Strunz No: VIII/C.14-50
Locality:

Notes: