Help mindat.org|Log In|Register|
Home PageMindat NewsThe Mindat ManualHistory of MindatCopyright StatusManagement TeamContact UsAdvertise on Mindat
Donate to MindatSponsor a PageSponsored PagesTop Available PagesMindat AdvertisersAdvertise on MindatThe Mindat Store
Minerals by PropertiesMinerals by ChemistryRandom MineralSearch by minIDLocalities Near MeSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
Keyword(s):
 
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
StatisticsThe ElementsMember ListBooks & MagazinesMineral Shows & EventsThe Mindat DirectoryHow to Link to MindatDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery

Rokühnite

This page is currently not sponsored. Click here to sponsor this page.
Formula:
FeCl2 · 2H2O
System:
Monoclinic
Colour:
Colourless (transmitted ...
Name:
Named after Robert Kühn, professor of mineralogy.
The hydrated counterpart of lawrencite. Other approved ferrous-iron-bearing chlorides include droninoite and hibbingite. Compare the hydrated ferric-iron chloride minerals: 'hydromolysite', 'Unnamed (Fe Chloride Hydrate I)', and 'Unnamed (Fe Chloride Hydrate II)'.

Crystal structure (synthetic material) details/elements:
- polymeric chains of iron and chlorine ions, near‐square planar configuration
- 2 iron ions share single Cl ion
- water groups fill the remaining octahedral positions about the iron ion
- hydrogen bonds involving water groups link adjacent chains, in direction || c.

Classification of Rokühnite

Approved
3.BB.10

3 : HALIDES
B : Simple halides, with H2O
B : M:X = 1:2
9.2.4.1

9 : NORMAL HALIDES
2 : AX2
8.11.3

8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
11 : Halides of Fe and Ni
mindat.org URL:
http://www.mindat.org/min-3440.html
Please feel free to link to this page.

Type Occurrence of Rokühnite

General Appearance of Type Material:
rare thin plates, commonly comprising fibers, with dominating {110} form and a number of other forms present, up to 300 µm
Geological Setting of Type Material:
secondary, in fissures within earlier K-rich salt beds
Associated Minerals at Type Locality:

Physical Properties of Rokühnite

Diaphaneity (Transparency):
Transparent
Colour:
Colourless (transmitted light), light green
Comment:
brown when oxidized
Comment:
not determined
Tenacity:
Flexible
Cleavage:
Very Good
{100}; also good on {010}
Density:
2.35 g/cm3 (Measured)    2.35 g/cm3 (Calculated)

Crystallography of Rokühnite

Crystal System:
Monoclinic
Cell Parameters:
a = 7.396(1) Å, b = 8.458(2) Å, c = 3.638(1) Å
β = 97.68(2)°
Ratio:
a:b:c = 0.874 : 1 : 0.43
Unit Cell Volume:
V 225.54 ų (Calculated from Unit Cell)
Z:
2
Twinning:
contact, on {201}
Comment:
C2/m, C2 or Cm
X-Ray Powder Diffraction Data:
d-spacingIntensity
5.536 (100)
2.762 (74)
4.228 (62)
2.415 (55)
2.892 (54)
2.744 (30)
2.096 (30)

Optical Data of Rokühnite

Type:
Biaxial (+)
RI values:
nα = 1.605 nβ = 1.633 nγ = 1.702
2V:
Measured: 64° , Calculated: 68°
Max Birefringence:
δ = 0.097
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
strong (r ≤ v)

Chemical Properties of Rokühnite

Formula:
FeCl2 · 2H2O
All elements listed in formula:
Analytical Data:
A mixture analysis; the mixture comprises [%]: 8.89 carnallite, 18.47 rinneite, 23.55 halite, 1.02 tachyhydrite, and 48.14 rokühnite
FeO 22.46
MgO 2.94
CaO 0.11
Na2O 13.89
K2O 7.89
Cl 50.05
H2O 14.58
-O=Cl2 11.29
insol. (HNO3) 0.06

total 100.69
Empirical Formula:
(Fe0.88Mg0.12)Σ1.00Cl2•1.95H2O
Common Impurities:
Mg

Relationship of Rokühnite to other Species

3.BB.05EriochalciteCuCl2 · 2H2O
3.BB.15BischofiteMgCl2 · 6H2O
3.BB.20NickelbischofiteNiCl2 · 6H2O
3.BB.25SinjariteCaCl2 · 2H2O
3.BB.30AntarcticiteCaCl2 · 6H2O
3.BB.35TachyhydriteCaMg2Cl6 · 12H2O
8.11.1MolysiteFeCl3
8.11.2HydromolysiteFeCl3 · 6H2O
8.11.4DouglasiteK2[Fe2+Cl4(OH2)2]
8.11.5ErythrosideriteK2[Fe3+Cl5(H2O)]
8.11.6RinneiteK3Na[FeCl6]
8.11.7Kremersite(NH4,K)2[Fe3+Cl5(H2O)]
8.11.8IowaiteMg6Fe23+(OH)16Cl2 · 4H2O
8.11.9NickelbischofiteNiCl2 · 6H2O
8.11.10Lawrencite(Fe2+,Ni)Cl2

Other Names for Rokühnite

Name in Other Languages:
German:Rokühnit
Spanish:Rokühnita

Other Information

Other Information:
water-soluble; topotactical hydration and rapid oxidation in air
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Rokühnite

Reference List:
Morosin, B., Graeber, E.J. (1965): Crystal Structures of Manganese(II) and Iron(II) Chloride Dihydrate. J. Chem. Phys.: 42: 898

von Hodenberg, R., von Struensee, G. (1980): Rokühnite, FeCl2•2H2O, a new mineral. Neues Jahrb. Mineral. Monatsh.: 125-130

American Mineralogist (1981): 66: 219.

Anthony, J.W., Bideaux, R.A., Bladh, K.W. and Nichols, M.C., Eds. Handbook of Mineralogy, Mineralogical Society of America, Chantilly, VA 20151-1110, USA. http://www.handbookofmineralogy.org/ (2016)

Internet Links for Rokühnite

Localities for Rokühnite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Czech Republic
 
  • Moravia (Mähren; Maehren)
    • Moravia-Silesia Region
      • Karviná
        • Orlová
Matýsek D., Jirásek J., Osovský M., Skupien P.. Minerals formed by the weathering of sulfides in mines of the Czech part of the Upper Silesian Basin. Mineralogical Magazine, 2014, 78, 5, 1265-1286.
Germany
 
  • Lower Saxony
    • Hildesheim
      • Diekholzen Potash works
Andreas Gerstenberg collection
      • Giesen
Aufschluss 1987(4), 114
Aufschluss 87/4
Poland
 
  • Upper Silesia (Śląskie)
    • Upper Silesian Coal Basin
      • Rybnik Coal Area
        • Radlin
Łukasz Kruszewski (2012) Unique chloride assemblage of exhalative origin from burning coal-mining dump in Radlin (Rybnik Coal Area, S Poland). Mineralogical Society of Poland Special Papers 40
Ukraine
 
  • Zhytomyr Oblast' (Zhitomir Oblast')
Lyckberg, P., Chornousenko, V. & Wilson, W. E. (2009): Volodarsk-Volynski, Zhitomir Oblast, Ukraine. Mineralogical Record, 40, 473-506.
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2016, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: July 28, 2016 19:20:51 Page generated: July 25, 2016 20:23:31
Go to top of page