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

Images:

Stilpnomelane

Comments: Golden metallic scaly stilpnomelane on pink orthoclase.
Location: French Creek No. 2 Mine, near Saint Peters, Chester County, Pennsylvania, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

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 - Pinacoidal H-M Symbol ( 1) Space Group: P1

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

By Intensity(I/I_o): 2.55(1), 4.16(1), 12.3(1),

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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Stilpnomelane

K(Fe++,Mg,Fe+++)8(Si,Al)12(O,OH)27•n(H2O)
Dana No: 74.01.01.01 Strunz No: 09.EG.40
Locality:

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