Cronstedtite Mineral Data

Cronstedtite Mineral Data +

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General Cronstedtite Information

Chemical Formula:

Fe++2Fe+++(SiFe+++)O5(OH)4

Composition:

Molecular Weight = 399.50 gm

Iron 55.92 % Fe 35.97 % FeO / 39.97 % Fe₂O₃

Silicon 7.03 % Si 15.04 % SiO₂

Hydrogen 1.01 % H 9.02 % H₂O

Oxygen 36.04 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Fe²⁺₂Fe³⁺₂SiO₅(OH)₄

IMA Status:

Valid Species (Pre-IMA) 1821

Locality:

Pribram and Kuttenberg, Bohemia of Czechoslovakia. Link to MinDat.org Location Data.

Cronstedtite Image

Images:

Cronstedtite

Comments: Pyramidal crystals of cronstedtite.
Location: Santa Eulalia, Chihuahua, Mexico. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Cronstedtite Crystallography

Axial Ratios:

a:c = 1:1.29329

Cell Dimensions:

a = 5.486, c = 7.095, Z = 1; V = 184.92 Den(Calc)= 3.59

Crystal System:

Trigonal - Ditrigonal PyramidalH-M Symbol (3m) Space Group: P 3₁m

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

By Intensity(I/I_o): 2.56(1), 7.1(0.9), 3.548(0.6),

Crystal Structure:

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Hendricks S B , American Mineralogist , 24 (1939) p.529-539, Random structures of layer minerals as illustrated by cronstedtite, (2FeO.Fe2O3.SiO2.2H2O). Possible iron content of kaolin

View Additional jPOWD Structure files for Cronstedtite
[1] [2] [3] [4]

Physical Properties of Cronstedtite

Cleavage:

[001] Perfect

Color:

Brownish black, Greenish black, Dark brown, Black.

Density:

3.34 - 3.35, Average = 3.34

Diaphaniety:

Transparent to translucent

Habit:

Amorphous - No crystalline form or imitative shape.

Habit:

Divergent - Crystals radiate from a center without producing stellar forms.

Habit:

Pyramidal - Crystals are shaped like pyramids.

Hardness:

3.5 - Copper Penny

Luster:

Vitreous - Resinous

Streak:

dark olive green

Optical Properties of Cronstedtite

Optical Data:

Biaxial (-), a=1.72, b=1.8, g=1.8, bire=0.0800, 2V(Calc)=0, 2V(Meas)=0.

Calculated Properties of Cronstedtite

Electron Density:

r_electron=3.49 gm/cc
note: r_Cronstedtite=3.59 gm/cc.

Fermion Index

Fermion Index = 0.01531
Boson Index = 0.98469

Photoelectric:

PE_Cronstedtite= 17.04 barns/electron
U=PE_Cronstedtite x r_electron= 59.43 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Cronstedtite is Not Radioactive

Cronstedtite Classification

Dana Class:

71.1.2c.7 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.1)with 1:1 layers

(71.1.2c)Serpentine group (Amesite subgroup)

71.1.2c.1 Amesite Mg2Al(SiAl)O5(OH)4 C1 1

71.1.2c.2 Berthierine (Fe,Fe,Al,Mg)2-3(Si,Al)2O5(OH)4 Cm m

71.1.2c.3 Brindleyite (Ni,Mg,Fe)2Al(SiAl)O5(OH)4 C 2 2

71.1.2c.4 Fraipontite (Zn,Al)3(Si,Al)2O5(OH)4 Cm m

71.1.2c.5 Kellyite (Mn,Mg,Al)3(Si,Al)2O5(OH)4 P 6₃ 6

71.1.2c.6 Manandonite Li2Al4[(Si2AlB)O10](OH)8 C1 1

71.1.2c.7 Cronstedtite Fe2Fe(SiFe)O5(OH)4 P 3₁m 3m

Strunz Class:

VIII/H.27-120 VIII - Silicates

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

VIII/H.27 - Serpentine group

VIII/H.27-10 Antigorite (Mg,Fe)3Si2O5(OH)4 Cm m

VIII/H.27-20 Lizardite Mg3Si2O5(OH)4 P1 1

VIII/H.27-30 Clinochrysotile Mg3Si2O5(OH)4 Cc, C 2/m Mono

VIII/H.27-40 Orthochrysotile Mg3Si2O5(OH)4 Unk Ortho

VIII/H.27-50 Parachrysotile Mg3Si2O5(OH)4 Unk Ortho

VIII/H.27-55 Caryopilite (Mn,Mg,Zn,Fe)3(Si,As)2O510(OH,Cl)4 Cm or C 2/m Mono

VIII/H.27-60 Greenalite (Fe,Fe)2-3Si2O5(OH)4 Unk Mono

VIII/H.27-70 Berthierine (Fe,Fe,Al,Mg)2-3(Si,Al)2O5(OH)4 Cm m

VIII/H.27-80 Fraipontite (Zn,Al)3(Si,Al)2O5(OH)4 Cm m

VIII/H.27-90 Zinalsite Zn2AlSi2O5(OH)4·2(H2O)(?) Mono

VIII/H.27-95 Dozyite (Mg7Al2)(Si4Al2)O15(OH)12 Cm m

VIII/H.27-100 Amesite Mg2Al(SiAl)O5(OH)4 C1 1

VIII/H.27-110 Kellyite (Mn,Mg,Al)3(Si,Al)2O5(OH)4 P 6₃ 6

VIII/H.27-120 Cronstedtite Fe2Fe(SiFe)O5(OH)4 P 3₁m 3m

VIII/H.27-140 Karpinskite (Mg,Ni)2Si2O5(OH)2(?) Unk Mono

VIII/H.27-150 Nepouite Ni3Si2O5(OH)4 Ccm21 mm2

VIII/H.27-160 Pecoraite Ni3Si2O5(OH)4 C 2/m 2/m

VIII/H.27-170 Brindleyite (Ni,Mg,Fe)2Al(SiAl)O5(OH)4 C 2 2

VIII/H.27-180 Maufite (Mg,Ni)Al4Si3O13·4(H2O)(?) Mono ? Mono

VIII/H.27-190 Carlosturanite (Mg,Fe,Ti,Mn)21(Si,Al)12O28(OH)34 Cm m

Other Cronstedtite Information

References:

NAME( Ford32) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

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Cronstedtite

Fe++2Fe+++(SiFe+++)O5(OH)4
Dana No: 71.1.2c.7 Strunz No: VIII/H.27-120
Locality:

Notes: