Stilpnomelane Mineral Data

General Stilpnomelane Information

Chemical Formula: K(Fe++,Mg,Fe+++)8(Si,Al)12(O,OH)27•n(H2O) Composition: Molecular Weight = 1,247.57 gm    Potassium   3.13 %  K    Magnesium   2.73 %  Mg    Aluminum    4.33 %  Al    Iron       29.54 %  Fe    Silicon    22.51 %  Si    Hydrogen    0.57 %  H    Oxygen     37.19 %  O              ______               100.00 %  Empirical Formula: KFe²⁺_4.3Mg_1.4Fe³⁺_2.3Si₁₀Al₂O₂₄(OH)₃·2(H₂O) Environment: Commonly associated with iron ores. IMA Status: Valid Species (Pre-IMA) 1827 Locality: Moravia of Czechoslovakia at Sternberg in a bed of limonite. Link to MinDat.org Location Data. Name Origin: From the Greek for "shining" and "black", in allusion to its luster and color. Name Pronunciation: Stilpnomelane + Pronunciation Synonym: Ferristilpnomelane - high Fe+++   Ferrostilpnomelane - Low Fe+++  

Stilpnomelane Image

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Stilpnomelane Crystallography

Axial Ratios: a:b:c =1:1:0.8073 Cell Dimensions: a = 21.8, b = 21.8, c = 17.6, Z = 6; alpha = 125.03°, beta = 95.98°, gamma = 120° V = 5,899.18 Den(Calc)= 2.11 Crystal System: Triclinic - PinacoidalH-M Symbol ( 1) Space Group: P1 X Ray Diffraction: By Intensity(I/I_o): 2.55(1), 4.16(1), 12.3(1), Crystal Structure:

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Guggenheim S , Eggleton R A , American Mineralogist , 79 (1994) p.438-442, Stilpnomelane and parsettensite: A distance least squares (DLS) study

 

Physical Properties of Stilpnomelane

Cleavage: {001} Perfect Color: Brown red, Green, Golden brown, Black. Density: 2.77 - 2.96, Average = 2.86 Diaphaneity: Subtranslucent to opaque Fracture: Brittle - Generally displayed by glasses and most non-metallic minerals. Habit: Fibrous - Crystals made up of fibers. Habit: Foliated - Two dimensional platy forms. Habit: Platy - Sheet forms (e.g. micas). Hardness: 3 - Calcite Luminescence: Non-fluorescent. Luster: Vitreous - Dull Streak: gray white  

Optical Properties of Stilpnomelane

Optical Data: Biaxial (-), a=1.543-1.634, b=1.576-1.745, g=1.576-1.745, bire=0.0330-0.1110, 2V(Calc)=0, 2V(Meas)=0-40. Dispersion none. Pleochroism (x): pale yellow, golden yellow, pale brown, or colorless. Pleochroism (y): deep brown, nearly black, chestnut brown, deep yellowish brown, or light greenish yellow. Pleochroism (z): deep brown, nearly black, chestnut brown, deep yellowish brown, or light greenish yellow.  

Calculated Properties of Stilpnomelane

Electron Density: Bulk Density (Electron Density)=2.46 gm/cc
note: Specific Gravity of Stilpnomelane =2.51 gm/cc.
Fermion Index: Fermion Index = 0.01
Boson Index = 0.99 Photoelectric: PE_{Stilpnomelane} = 10.10 barns/electron
U=PE_{Stilpnomelane} x r_electron= 24.89 barns/cc.
Radioactivity:

GRapi = 44.41 (Gamma Ray American Petroleum Institute Units)
Concentration of Stilpnomelane per GRapi unit = 2.25 (%)

Estimated Radioactivity from Stilpnomelane - barely detectable

 

Stilpnomelane Classification

Dana Class: 74.01.01.01 (74)Phyllosilicate Modulated Layers   (74.01)with joined islands   (74.01.01)Stilpnomelane group  

74.01.01.01 Stilpnomelane K(Fe,Mg,Fe)8(Si,Al)12(O,OH)27•n(H2O) P1 1

 

74.01.01.02 Lennilenapeite K6-7(Mg,Mn,Fe,Fe,Zn)48(Si,Al)72(O,OH)216•16(H2O) Unk (pseudo-HEX) Tri

 

74.01.01.03 Franklinphilite (K,Na)4(Mn,Mg,Zn)48(Si,Al)72(O,OH)216•6(H2O) pseudo-HEX P1 or P1 Tri

 

74.01.01.04 Bannisterite KCa(Mn,Fe,Zn,Mg)21(Si,Al)32O76(OH)16•4-12(H2O) A2/a 2/m

 

74.01.01.05 Middendorfite! K3Na2Mn5Si12(O,OH)36•2H2O P 2₁/m or P 2₁ Mono

Strunz Class: 09.EG.40 09 - SILICATES (Germanates)   09.E - Phyllosilicates   09.EG -Double nets with 6-membered and larger rings  

09.EG.40 Franklinphilite (K,Na)4(Mn,Mg,Zn)48(Si,Al)72(O,OH)216•6(H2O) pseudo-HEX P1 or P1 Tri

 

09.EG.40 Ekmanite? (Fe,Mg,Mn,Fe)3(Si,Al)4O10(OH)2•2(H2O) Unk Ortho

 

09.EG.40 Lennilenapeite K6-7(Mg,Mn,Fe,Fe,Zn)48(Si,Al)72(O,OH)216•16(H2O) Unk (pseudo-HEX) Tri

 

09.EG.40 Parsettensite (K,Na,Ca)(Mn,Al)7Si8O20(OH)8•2(H2O)(?) C 2/m 2/m

 

09.EG.40 Stilpnomelane K(Fe,Mg,Fe)8(Si,Al)12(O,OH)27•n(H2O) P1 1

 

Other Stilpnomelane Information

References: NAME( Ford32) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990) See Also: Links to other databases for Stilpnomelane :
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 - Minerals in Thin Section-University of North Carolina
13 - Minerals in Thin Sections-Humboldt State
14 - Online Mineral Museum
15 - QUT Mineral Atlas
16 - Ruff.Info
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