Rhomboclase Mineral Data

Rhomboclase Mineral Data +

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General Rhomboclase Information

Chemical Formula:

(H5O2)+Fe+++(SO4)2·2(H2O)

Composition:

Molecular Weight = 321.04 gm

Iron 17.40 % Fe 24.87 % Fe₂O₃

Hydrogen 2.83 % H 25.25 % H₂O

Sulfur 19.98 % S 49.88 % SO₃

Oxygen 59.80 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

HFe³⁺(SO₄)₂·4(H₂O)

IMA Status:

Valid Species (Pre-IMA) 1891

Locality:

Link to MinDat.org Location Data.

Synonym:

ICSD 4302

PDF 27-245

Rhomboclase Image

Images:

Rhomboclase

Comments: Platy crystal rhomboclase spray.
Location: Rio Tinto, Andalucia, Spain. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Rhomboclase Crystallography

Axial Ratios:

a:b:c =0.5314:1:0.2964

Cell Dimensions:

a = 9.723, b = 18.295, c = 5.424, Z = 4; V = 964.83 Den(Calc)= 2.21

Crystal System:

Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: P nma

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

By Intensity(I/I_o): 3.113(1), 3.331(0.45), 4.05(0.45),

Forms:

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Forms: [ 0 2 1] [ 0 1 0] [ 1 1 0] [ 1 1 1] [ 0 0 1]

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Crystal Structure:

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Mereiter K , Tschermaks Mineralogische und Petrographische Mitteilungen , 21 (1974) p.216-232, Die kristallstruktur von rhomboklas, H5O2+{Fe[SO4]2*2H2O}-, Note: synthetic crystal

View Additional jPOWD Structure files for Rhomboclase
[1]

Physical Properties of Rhomboclase

Cleavage:

[001] Perfect, [110] Good

Color:

Bluish, Colorless, Greenish, Gray, Yellow.

Density:

2.23

Diaphaniety:

Transparent

Fracture:

Conchoidal - Uneven - Uneven fracture producing small, conchoidal fragments.

Hardness:

2 - Gypsum

Luster:

Vitreous - Pearly

Streak:

white

Optical Properties of Rhomboclase

Gladstone-Dale:

CI meas= -0.021 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= -0.03 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2602,KPDmeas= 0.2578,KC= 0.2525

Optical Data:

Biaxial (+), a=1.534, b=1.553, g=1.638, bire=0.1040, 2V(Calc)=54, 2V(Meas)=27.

Calculated Properties of Rhomboclase

Electron Density:

r_electron=2.26 gm/cc
note: r_Rhomboclase=2.23 gm/cc.

Fermion Index

Fermion Index = 0.00547
Boson Index = 0.99453

Photoelectric:

PE_Rhomboclase= 6.27 barns/electron
U=PE_Rhomboclase x r_electron= 14.21 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Rhomboclase is Not Radioactive

Rhomboclase Classification

Dana Class:

29.1.1.1 (29)Hydrated Acid and Sulfates

(29.1)(Hydrated, Acid)

(29.1.1)Dana Group

29.1.1.1 Rhomboclase (H5O2)Fe(SO4)2·2(H2O) P nma 2/m 2/m 2/m

Strunz Class:

VI/C.08-10 VI - Sulfates,Chromates,Molybdates and Tungstates

VI/C - Water-bearing sulfates without unfamiliar anions. cations of medium size

VI/C.08 - Rhomboclase - Meta-alunogen series

VI/C.08-10 Rhomboclase (H5O2)Fe(SO4)2·2(H2O) P nma 2/m 2/m 2/m

VI/C.08-20 Lausenite Fe2(SO4)3·6(H2O) Unk. Mono

VI/C.08-30 Kornelite Fe2(SO4)3·7(H2O) P 2₁/c 2/m

VI/C.08-40 Coquimbite Fe2(SO4)3·9(H2O) P 3c 3 2/m

VI/C.08-50 Paracoquimbite Fe2(SO4)3·9(H2O) R 3 3

VI/C.08-60 Quenstedtite Fe2(SO4)3·10(H2O) P1 1

VI/C.08-70 Alunogen Al2(SO4)3·17(H2O) P1 1

VI/C.08-80 Meta-alunogen Al4(SO4)6·27(H2O) Mono

Other Rhomboclase Information

References:

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

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Rhomboclase

(H5O2)+Fe+++(SO4)2·2(H2O)
Dana No: 29.1.1.1 Strunz No: VI/C.08-10
Locality:

Notes: