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Akrochordite

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About AkrochorditeHide

Formula:
(Mn2+,Mg)5(AsO4)2(OH)4 · 4H2O
Colour:
Yellowish red-brown, pale to dark brown, pale pink,
Lustre:
Sub-Vitreous, Resinous, Dull
Hardness:
Specific Gravity:
3.194 - 3.35
Crystal System:
Monoclinic
Name:
Named by Gustav Flink in 1922 from Greek ακρόχορδον (akrochordon) = "a wart," in allusion to the appearance of its form of aggregation.
Isostructural with:
A rare (Mn,Mg)-arsenate isotypic with Guanacoite.


Classification of AkrochorditeHide

Approved, 'Grandfathered' (first described prior to 1959)
8.DD.10

8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
D : With only medium-sized cations, (OH, etc.):RO4= 2:1
42.4.1.1

42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
4 : (AB)5(XO4)2Zq·xH2O
20.8.11

20 : Arsenates (also arsenates with phosphate, but without other anions)
8 : Arsenates of Mn

Physical Properties of AkrochorditeHide

Sub-Vitreous, Resinous, Dull
Transparency:
Translucent
Colour:
Yellowish red-brown, pale to dark brown, pale pink,
Hardness:
3½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
On {010} , perfect; a second, perpendicular to the first.
Density:
3.194 - 3.35 g/cm3 (Measured)    3.26 g/cm3 (Calculated)

Optical Data of AkrochorditeHide

Type:
Biaxial (+)
RI values:
nα = 1.672 nβ = 1.676 nγ = 1.683
2V:
Measured: 45°
Birefringence:
0.011
Max Birefringence:
δ = 0.011
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
r < v relatively strong
Optical Extinction:
Y^c ~ 45°, X = b
Pleochroism:
Non-pleochroic

Chemical Properties of AkrochorditeHide

Formula:
(Mn2+,Mg)5(AsO4)2(OH)4 · 4H2O
IMA Formula:
Mn2+5(AsO4)2(OH)4 · 4H2O

Crystallography of AkrochorditeHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/c
Cell Parameters:
a = 5.682 Å, b = 17.627 Å, c = 6.832 Å
β = 99.5°
Ratio:
a:b:c = 0.322 : 1 : 0.388
Unit Cell V:
674.89 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Crystals are prismatic to lathlike, elongated along [201], generally splayed or tapered, to 2 mm; may be in radial aggregates and subparallel sheaves. Typically as wartlike or spherical aggregates of minute crystals.

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
8.79 (80)
5.31 (35)
4.40 (100)
3.62 (40)
3.112 (35)
3.062 (35)
2.750 (50)

Type Occurrence of AkrochorditeHide

General Appearance of Type Material:
Small, rounded wartlike aggregates
Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, 162614, R5396.
Geological Setting of Type Material:
A rare mineral in hausmannite ore from a metamorphosed Fe–Mn orebody
Associated Minerals at Type Locality:
Reference:
Flink, G. (1922) Akrochordit, ett nytt mineral från Långbans gruvor. Geologiska Föreningens i Stockholm Förhandlinger: 44: 773-776.

Synonyms of AkrochorditeHide

Other Language Names for AkrochorditeHide

Common AssociatesHide

Chlorophoenicite(Mn,Mg)3Zn2(AsO4)(OH,O)6
SarkiniteMn2+2(AsO4)(OH)
Associated Minerals Based on Photo Data:
Eveite6 photos of Akrochordite associated with Eveite on mindat.org.
Manganohörnesite1 photo of Akrochordite associated with Manganohörnesite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

8.DD.05ChenevixiteCu2Fe3+2(AsO4)2(OH)4Mon. 2/m : P21/m
8.DD.05LuetheiteCu2Al2(AsO4)2(OH)4Mon. 2/m : P21/m
8.DD.10GuanacoiteCu2Mg3(AsO4)2(OH)4 · 4H2OMon. 2/m : P21/b
8.DD.15Aheylite(Fe2+,Zn)Al6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15ChalcosideriteCuFe3+6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15Faustite(Zn,Cu)Al6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15PlaneriteAl6(PO4)2(HPO4)2(OH)8 · 4 H2OTric. 1 : P1
8.DD.15TurquoiseCu(Al,Fe3+)6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15AfmiteAl3(OH)4(H2O)3(PO4)(PO3OH) · H2OTric. 1 : P1
8.DD.20ChildreniteFe2+Al(PO4)(OH)2 · H2OOrth. mm2 : Ccc2
8.DD.20EosphoriteMn2+Al(PO4)(OH)2 · H2OOrth. mmm (2/m 2/m 2/m) : Cmca
8.DD.20Ernstite(Mn2+,Fe3+)Al(PO4)(OH,O)2 · H2OMon.

Related Minerals - Dana Grouping (8th Ed.)Hide

42.4.1.2GuanacoiteCu2Mg3(AsO4)2(OH)4 · 4H2OMon. 2/m : P21/b

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

20.8.1SarkiniteMn2+2(AsO4)(OH)Mon. 2/m : P2/m
20.8.2EveiteMn2+2(AsO4)(OH)Orth. mmm (2/m 2/m 2/m) : Pnnm
20.8.3ArsenoclasiteMn2+5(AsO4)2(OH)4Orth.
20.8.4FlinkiteMn2+2Mn3+(AsO4)(OH)4Orth.
20.8.5JarosewichiteMn2+3Mn3+(AsO4)(OH)6Orth. 2 2 2
20.8.6AllactiteMn2+7(AsO4)2(OH)8Mon. 2/m : P21/b
20.8.7KrautiteMn(HAsO4) · H2OMon. 2 : P21
20.8.8SynadelphiteMn2+9(As5+O4)2(As3+O3)(OH)9 · 2H2OOrth. mmm (2/m 2/m 2/m) : Pnma
20.8.9SterlinghilliteMn3(AsO4)2 · 4H2OTric. 1 : P1
20.8.10GeigeriteMn2+5(AsO4)2(HAsO4)2 · 10H2OTric.
20.8.12Manganohörnesite(Mn,Mg)3(AsO4)2 · 8H2OMon. 2/m : P2/m
20.8.13FluckiteCaMn2+(HAsO4)2 · 2H2OTric. 1 : P1
20.8.14BrandtiteCa2(Mn2+,Mg)(AsO4)2 · 2H2OMon. 2/m : P21/b
20.8.15ParabrandtiteCa2Mn2+(AsO4)2 · 2H2OTric.
20.8.16WallkilldelliteCa2Mn2+3(AsO4)2(OH)4 · 9H2OHex.
20.8.17Berzeliite(NaCa2)Mg2(AsO4)3Iso. m3m (4/m 3 2/m) : Ia3d
20.8.18ManganberzeliiteNaCa2Mn2+2(AsO4)3Iso. m3m (4/m 3 2/m) : Ia3d
20.8.19Magnesiochlorophoenicite(Mg,Mn)3Zn2(AsO4)(OH,O)6Mon. 2/m : B2/m
20.8.20VillyaelleniteMnMn2Ca2(AsO4)2(HAsO4)2 · 4H2OMon. 2/m : B2/b
20.8.21Hematolite(Mn,Mg,Al,Fe3+)15(As5+O4)2(As3+O3)(OH)23Trig. 3 : R3
20.8.22GrischuniteNaCa2Mn2+5Fe3+(AsO4)6 · 2H2OOrth.

Fluorescence of AkrochorditeHide

Not fluorescent

Other InformationHide

Notes:
Readily soluble in dilute H2SO4, yielding a purple (lilac) solution.
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 AkrochorditeHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Flink, G. (1922) Akrochordit, ett nytt mineral från Långbans gruvor. Geologiska Föreningens i Stockholm Förhandlinger: 44: 773-776.
Almström, G.K. (1923) Om akrochorditens kemiska sammensätning. Geologiska Föreningens i Stockholm Förhandlinger: 45: 117-118.
Shannon, E.V., Wherry, E.T. (1923) New minerals: doubtful species. American Mineralogist: 8: 167-169.
Barth and Berman (1930) Chemie der Erde, Jena: 5: 41.
Palache, C., Berman, H., Frondel, C. (1951) The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 927.
Moore, P.B. (1968) Contributions to Swedish mineralogy. I. Studies on the basic arsenates of manganese: retzian, hemafibrite, synadelphite, arsenoclasite, arseniopleite, and akrochordite. Arkiv. Mineral. Geol.: 4(5): 425–444.
Fleischer, M.(1968) New mineral names. American Mineralogist: 53: 1779.
Welin, E. (1968) Notes on the mineralogy of Sweden 6. X-ray powder data for minerals from Långban and the related mineral deposits of Central Sweden.Arkiv för Mineralogi och Geologi: 4(30): 499-541.
Moore, P.B., Sen Gupta, P.K., Schlemper, E.O. (1989) Akrochordite, (Mn,Mg)5(OH)4(H2O)4(AsO4)2: A sheet structure with amphibole walls. American Mineralogist: 74: 256-262.
Gaines, Richard V., H. Catherine W. Skinner, Eugene E. Foord, Brian Mason, Abraham Rosenzweig, Vandall King (1997), Dana's New Mineralogy : The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, 8th. edition.

Internet Links for AkrochorditeHide

Localities for AkrochorditeHide

This 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.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Australia
 
  • Western Australia
    • Meekatharra Shire
      • Milgun Station
Peter Downes, WA Museum
Germany
 
  • Lower Saxony
    • Harz
      • Bad Grund
        • Wiemannsbucht
Haack, U., Schnorrer-Koehler, G. & Lueders, V. (1987): Seltenerd-Minerale aus hydrothermalen Gängen des Harzes. Chemie der Erde 47, 41-45 (in German).
Sweden
 
  • Värmland
    • Filipstad
Geologiska Föreningens I Stockholm. Förhandlinger, Stockholm (1922) 44, 773; Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 927; Nysten, P., Holtstam, D. and Jonsson, E. (1999) The Långban minerals. In Långban - The mines,their minerals, geology and explorers (D. Holtstam and J. Langhof, eds.), Swedish Museum of Natural History and Raster Förlag, Stockholm & Chr. Weise Verlag, Munich, pp. 89-183.
Flink, G. (1922): Akrochordit, ett nytt mineral från Långbans gruvor. Geologiska Föreningens i Stockholm Förhandlinger. 44: 773-776.
      • Nordmark Odal Field (Nordmarksberg)
Langhof, J. (1998): Akrochordit från Nordmark. Långbansnytt. vol 12. [ reprinted in: Långbansnytt. De första 20 åren 1983-2003. Långbansällskapet - Skrifter och rapporter. 2, 42-43];
USA
 
  • New Jersey
    • Sussex Co.
      • Franklin mining district
        • Ogdensburg
          • Sterling Hill
Dunn, P.J. (1981) Mineralogical Magazine: 44: 235-236; Dunn, Pete J. (1995): Franklin and Sterling Hill New Jersey: the world’s most magnificent mineral deposits, part : 5: 655-656.
Mineral and/or Locality  
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