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Stichtite-2H

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Formula:
Mg6(Cr,Al)2(CO3)(OH)16 · 4H2O
System:
Hexagonal
Colour:
Intense violet to ...
Hardness:
1½ - 2
Name:
For the type locality, Barberton District, Transvaal, South Africa.
A polytype of Stichtite

Originally named barbertonite. Recognised as a polytype of stichtite and accordingly discredited (Mills et al., 2011, 2012).

Classification of Stichtite-2H

5.DA.45

5 : CARBONATES (NITRATES)
D : Carbonates with additional anions, with H2O
A : With medium-sized cations
16b.6.1.2

16b : HYDRATED CARBONATES CONTAINING HYDROXYL OR HALOGEN
6 : AmBn(XO3)pZqxH2O & with (m+n):p = 8:1
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First Recorded Occurrence of Stichtite-2H

General Appearance of First Recorded Material:
Platy crystals, fibrous matted masses and cross-fiber veinlets
Place of Conservation of First Recorded Material:
Harvard University, Cambridge, Massachusetts, USA (No. 92549)
Year of Discovery:
1940
Geological Setting of First Recorded Material:
Alteration products of chromite in serpentinite
Associated Minerals at First Recorded Locality:

Physical Properties of Stichtite-2H

Waxy, Pearly
Diaphaneity (Transparency):
Transparent
Colour:
Intense violet to rose-pink; violet to light rose-pink in transmitted light
Streak:
Very pale violet to white
Hardness (Mohs):
1½ - 2
Tenacity:
Elastic
Cleavage:
Perfect
on {0001}
Density:
2.05 - 2.15 g/cm3 (Measured)    2.11 g/cm3 (Calculated)

Crystallography of Stichtite-2H

Crystal System:
Hexagonal
Cell Parameters:
a = 6.17Å, c = 15.52Å
Ratio:
a:c = 1 : 2.515
Unit Cell Volume:
V 511.67 ų (Calculated from Unit Cell)
Z:
1
Morphology:
Platy crystals, flattened on {0001}. Massive, in matted or contorted masses of fibers or plates; alos as cross-fiber veinlets.

Optical Data of Stichtite-2H

Type:
Uniaxial (-)
RI values:
nω = 1.557 nε = 1.529
Max Birefringence:
δ = 0.028
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Pleochroism:
Weak
Comments:
O = dark rose-pink to violet
E = light rose-pink to violet

Chemical Properties of Stichtite-2H

Formula:
Mg6(Cr,Al)2(CO3)(OH)16 · 4H2O
Essential elements:
All elements listed in formula:
Analytical Data:
Intimately intermixed with stichtite; analyses of pure material are therefore lacking. The species is supported by X-ray diffraction patterns showing group membership.

Relationship of Stichtite-2H to other Species

5.DA.05DypingiteMg5(CO3)4(OH)2 · 5H2O
5.DA.05GiorgiositeMg5(CO3)4(OH)2 · 5-6H2O
5.DA.05HydromagnesiteMg5(CO3)4(OH)2 · 4H2O
5.DA.05WidgiemoolthaliteNi5(CO3)4(OH)2 · 5H2O
5.DA.05UM1986-10-CO:ClHMgMnZnMg5(Zn,Mn)3(CO3)2(OH,Cl)12 · H2O
5.DA.05UM1987-01-CO:HMgSMg4(CO3)2(OH)2 · 6H2O ?
5.DA.10ArtiniteMg2(CO3)(OH)2 · 3H2O
5.DA.10IndigiriteMg2Al2(CO3)4(OH)2 · 15H2O
5.DA.10ChlorartiniteMg2(CO3)(OH)Cl · 2H2O
5.DA.15OtwayiteNi2(CO3)(OH)2 · H2O
5.DA.15ZaratiteNi3(CO3)(OH)4 · 4H2O
5.DA.20KambaldaiteNaNi4(CO3)3(OH)3 · 3H2O
5.DA.25CallaghaniteCu2Mg2(CO3)(OH)6 · 2H2O
5.DA.30Claraite(Cu,Zn)3(CO3)(OH)4 · 4H2O
5.DA.35HydroscarbroiteAl14(CO3)3(OH)36 · nH2O
5.DA.35ScarbroiteAl5(CO3)(OH)13 · 5H2O
5.DA.40CaresiteFe42+Al2(OH)12[CO3] · 3H2O
5.DA.40QuintiniteMg4Al2(OH)12[CO3] · 3H2O
5.DA.40CharmariteMn42+Al2(OH)12[CO3] · 3H2O
5.DA.45BrugnatelliteMg6Fe3+(CO3)(OH)13 · 4H2O
5.DA.45ChlormagaluminiteMg4Al2(OH)12Cl2 · 3H2O
5.DA.45Hydrotalcite-2HMg6Al2(CO3)(OH)16 · 4H2O
5.DA.45Pyroaurite-2HMg6Fe23+(CO3)(OH)16 · 4H2O
5.DA.45ZaccagnaiteZn4Al2(OH)12[CO3] · 3H2O
5.DA.50ComblainiteNi4Co2(OH)12[CO3] · 3H2O
5.DA.50DesautelsiteMg6Mn23+(OH)16[CO3] · 4H2O
5.DA.50HydrotalciteMg6Al2(OH)16[CO3] · 4H2O
5.DA.50PyroauriteMg6Fe23+(OH)16[CO3] · 4H2O
5.DA.50ReevesiteNi6Fe23+(OH)16(CO3) · 4H2O
5.DA.50StichtiteMg6Cr2(OH)16[CO3] · 4H2O
5.DA.50TakoviteNi6Al2(OH)16[CO3] · 4H2O
5.DA.50UM1998-10-CO:CoHNiCo6Fe2(CO3)(OH)16 · 4H2O ?
5.DA.55CoalingiteMg10Fe23+(OH)24[CO3] · 2H2O

Other Names for Stichtite-2H

Name in Other Languages:
Bosnian (Cyrillic Script):Stichtite-2H
Spanish:Barbertonita

Other Information

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 Stichtite-2H

Reference List:
Read and Dixon (1933), Mineralogical Magazine: 23: 309.

Mineralogical Society of America Annual Meeting, Program Abstracts, 1940, 6.

Frondel, C. (1941): Constitution and polymorphism of the pyroaurite and sjögrenite groups. American Mineralogist 26, 295-315.

Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 659.

Taylor, H. W. F. (1973): Crystal structures of some double hydroxide minerals. Mineralogical Magazine 39, 377-389.

Anthony, J. W. et al. (1997): Handbook of Mineralogy, Vol. 3, 39.

Mills, S. J., Whitfield, P. S., Wilson, S. A., Woodhouse, J. A., Dipple, G. M., Raudsepp, M. & Francis, C. A. (2011) The crystal structure of stitchtite, re-examination of barbertonite and the nature of polytypism in MgCr hydrotalcites. American Mineralogist, 96(1), 179–187.

Mills, S.J., Christy, A.G., Genin, J.-M.R., Kameda, T., Colombo, F. (2012): Nomenclature of the hydrotalcite supergroup: natural layered double hydroxides. Mineralogical Magazine, 76, 1289-1336.

Internet Links for Stichtite-2H

Localities for Stichtite-2H

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.
Australia
 
  • Tasmania
    • Zeehan district
      • North Dundas
R Bottrill, unpublished data
Czech Republic
 
  • Moravia (Mähren; Maehren)
    • South Moravia Region
      • Letovice (Lettowitz)
Ulrych, J.: Stichtit z hadcového tělesa od Slatinky u Letovic. Časopis pro mineralogii a geologii, 1966, roč. 11, č. 3, s. 311-315.
New Zealand
 
  • North Island
    • Manawatu-Wanganui
      • Tararua
        • Maharahara
Railton, G.L. & Watters, W.A. (1990): Minerals of New Zealand
South Africa
 
  • Mpumalanga Province
    • Ehlanzeni District
Am Min 26 (1941), 295
        • Kaapsche Hoop (Kaapsehoop)
Rocks & Min.: 21:275.
UK
 
  • Scotland
    • Shetland Islands
      • Mainland
        • Cunningsburgh
Anthony, J. W. et al. (1997): Handbook of Mineralogy, Vol. 3, 39
Mineral and/or Locality  
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