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About AkrochorditeHide

(Mn2+,Mg)5(AsO4)2(OH)4 · 4H2O
Yellowish red-brown, pale to dark brown, pale pink,
Sub-Vitreous, Resinous, Dull
Specific Gravity:
3.194 - 3.35
Crystal System:
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)

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

4 : (AB)5(XO4)2Zq·xH2O

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

Physical Properties of AkrochorditeHide

Sub-Vitreous, Resinous, Dull
Yellowish red-brown, pale to dark brown, pale pink,
3½ on Mohs scale
On {010} , perfect; a second, perpendicular to the first.
3.194 - 3.35 g/cm3 (Measured)    3.26 g/cm3 (Calculated)

Optical Data of AkrochorditeHide

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

Chemical Properties of AkrochorditeHide

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

Crystallography of AkrochorditeHide

Crystal System:
Class (H-M):
2/m - Prismatic
Space Group:
Cell Parameters:
a = 5.682 Å, b = 17.627 Å, c = 6.832 Å
β = 99.5°
a:b:c = 0.322 : 1 : 0.388
Unit Cell V:
674.89 ų (Calculated from Unit Cell)
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:
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:
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

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 · 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
20.8.4FlinkiteMn2+2Mn3+(AsO4)(OH)4Orth. mmm (2/m 2/m 2/m)
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
20.8.9SterlinghilliteMn2+3(AsO4)2 · 3H2OTric. 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
20.8.14BrandtiteCa2Mn2+(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

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.
  • Western Australia
    • Meekatharra Shire
      • Milgun Station
Peter Downes, WA Museum
  • 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).
  • Värmland County
    • 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];
  • 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.
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