Rhomboclase Mineral Data

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)

Environment:

Secondary mineral formed by alteration of pyrite, especially in an arid climate; typically of post-mining origin.

IMA Status:

Valid Species (Pre-IMA) 1891

Locality:

Smolnik (Szomolnok), 16 km northeast of Roznava, Slovakia. Link to MinDat.org Location Data.

Name Origin:

Named from the Greek for rhomb, for the typical rhombic crystal outline, and for to break, for its perfect cleavage.

Name Pronunciation:

Rhomboclase + Pronunciation

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 - Dipyramidal H-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),

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Forms: ( 0 2 1) ( 0 1 0) ( 1 1 0) ( 1 1 1) ( 0 0 1)

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Physical Properties of Rhomboclase

Cleavage:

{001} Perfect, {110} Good

Color:

Bluish, Colorless, Greenish, Gray, Yellow.

Density:

2.23

Diaphaneity:

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
Ncalc = 1.56

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:

Bulk Density (Electron Density)=2.26 gm/cc
note: Specific Gravity of Rhomboclase =2.23 gm/cc.

Fermion Index:

Fermion Index = 0.0054773418
Boson Index = 0.9945226582

Photoelectric:

PE_Rhomboclase= 6.27 barns/electron
U=PE_Rhomboclase x rElectron Density= 14.21 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Rhomboclase is Not Radioactive

Rhomboclase Classification

Dana Class:

29.01.01.01 (29)Hydrated Acid and Sulfates

(29.01)(Hydrated, Acid)

(29.01.01)Dana Group

29.01.01.01 Rhomboclase (H5O2)Fe(SO4)2•2(H2O) P nma 2/m 2/m 2/m

Strunz Class:

07.CB.55 07 - SULFATES (SELENATES, TELLURATES)

07.C - Sulfates (selenates, etc.) without Additional Anions, with H2O

07.CB -With only medium-sized cations

07.CB.55 Rhomboclase (H5O2)Fe(SO4)2•2(H2O) P nma 2/m 2/m 2/m

Other Rhomboclase Information

References:

NAME( AntBidBlaNic5) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

Links to other databases for Rhomboclase :
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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Rhomboclase

(H5O2)+Fe+++(SO4)2•2(H2O)
Dana No: 29.01.01.01 Strunz No: 07.CB.55
Locality:

Notes:

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