Fenaksite Mineral Data
General Fenaksite Information
Chemical Formula:
(K,Na,Ca)4(Fe++,Fe+++,Mn)2Si8O20(OH,F)
Composition:
Molecular Weight = 806.42 gm
Potassium 8.73 % K 10.51 % K2 O
Sodium 4.28 % Na 5.76 % Na2 O
Calcium 3.48 % Ca 4.87 % CaO
Manganese 2.04 % Mn 2.64 % MnO
Iron 11.77 % Fe 11.58 % FeO / 3.96 % Fe2 O3
Silicon 27.86 % Si 59.61 % SiO2
Hydrogen 0.10 % H 0.89 % H2 O
Oxygen 41.27 % O
Fluorine 0.47 % F 0.47 % F
- %
F -0.20 % -O=F2
______ ______
100.00 % 100.10 % = TOTAL OXIDE
Empirical Formula:
K1.8 Na1.5 Ca0.7 Fe2+ 1.3 Fe3+ 0.4 Mn2+ 0.3 Si8 O20 (OH)0.8 F0.2
Environment:
In pegmatites associated with an ijolite-urtite intrusion in a differentiated alkalic massif.
IMA Status:
Approved IMA 1959
Locality:
On Mts. Rasvumchorr and Yukspor, Khibiny massif, Kola Peninsula, Russia. Link to MinDat.org Location Data.
Name Origin:
Named for the Fe, Na, K, and Si in the formula.
Name Pronunciation:
Fenaksite + Pronunciation
Synonym:
ICSD 20098
PDF 13-520
Fenaksite Image
Images:
Fenaksite Crystallography
Axial Ratios:
a:b:c =0.847:1:1.2111
Cell Dimensions:
a = 6.98, b = 8.24, c = 9.98, Z = 1; alpha = 114.2°, beta = 80.22°, gamma = 115.6° V = 465.30 Den(Calc)= 2.88
Crystal System:
Triclinic - Pinacoidal H-M Symbol ( 1 ) Space Group: P1
X Ray Diffraction:
By Intensity(I/Io ): 3.03(1), 2.46(0.7), 3.55(0.7),
Physical Properties of Fenaksite
Cleavage:
{100} Good, {010} Good
Color:
Brown, Light pink.
Density:
2.744
Diaphaneity:
Transparent to Translucent
Habit:
Granular - Generally occurs as anhedral to subhedral crystals in matrix.
Hardness:
5-5.5 - Apatite-Knife Blade
Luster:
Pearly
Streak:
white
Optical Properties of Fenaksite
Gladstone-Dale:
CI meas = 0.028 (Excellent) - where the CI = (1-KPDmeas /KC ) CI calc = 0.061 (Fair) - where the CI = (1-KPDcalc /KC )
KPDcalc = 0.1958,KPDmeas = 0.2026,KC = 0.2085 Ncalc = 1.57 - 1.59
Optical Data:
Biaxial (+), a=1.541, b=1.56, g=1.567, bire=0.0260, 2V(Calc)=60, 2V(Meas)=84.
Calculated Properties of Fenaksite
Electron Density:
Bulk Density (Electron Density)=2.70 gm/cc note: Specific Gravity of Fenaksite =2.74 gm/cc.
Fermion Index:
Fermion Index = 0.01 Boson Index = 0.99
Photoelectric:
PEFenaksite = 6.44 barns/electronU=PEFenaksite x r electron = 17.41 barns/cc.
Radioactivity:
GRapi = 124.09 (Gamma Ray American Petroleum Institute Units)
Concentration of Fenaksite per GRapi unit = 0.81 (%)
Estimated Radioactivity from Fenaksite - barely detectable
Fenaksite Classification
Dana Class:
70.01.01.02 (70) Inosilicate Column or Tube Structures
(70.01) with columnar silicate units
(70.01.01) Litidionite group
70.01.01.01 Litidionite KNaCuSi4O10 P1 1
70.01.01.02 Fenaksite (K,Na,Ca)4(Fe,Fe,Mn)2Si8O20(OH,F) P1 1
70.01.01.03 Manaksite KNaMnSi4O10 P1 1
70.01.01.04 Agrellite NaCa2Si4O10F P1 1
Strunz Class:
09.DG.70 09 - SILICATES (Germanates)
09.D - Inosilicates* Structural terminology according to Liebau (1985)
09.DG -Inosilicates with 3-periodic single and multiple chains
09.DG.70 Fenaksite (K,Na,Ca)4(Fe,Fe,Mn)2Si8O20(OH,F) P1 1
09.DG.70 Manaksite KNaMnSi4O10 P1 1
Other Fenaksite Information
References:
NAME( AntBidBlaNic2) PHYS. PROP.(AntBidBlaNic2) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)
See Also:
Links to other databases for Fenaksite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info
15 - WWW-MINCRYST
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Print or Cut-and-Paste your Fenaksite Specimen Label here :
Fenaksite
(K,Na,Ca)4(Fe++,Fe+++,Mn)2Si8O20(OH,F)
Dana No: 70.01.01.02 Strunz No: 09.DG.70
Locality:
Notes:
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