Mindat Logo
Home Page Log In Message Board The Mindat Directory
Register Search Pages Chat Now! (2 online) Mindat Auctions

Akrochordite

Big Photo

Långban, Filipstad, Värmland, Sweden
© Knut Eldjarn

Formula:
(Mn
2+
 
,Mg)
 
5
[(OH)
 
2
|AsO
 
4
]
 
2
 · 4H
 
2
O
System:MonoclinicColour:reddish brown with a ...
Hardness:3½
Name:From Greek άκροχορδώυ akrochordon = "a wart," in allusion to the appearance of its form of aggregation.


A rare (Mn,Mg)-arsenate isotypic with Guanacoite.

Classification of Akrochordite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:7/D.16-30
Nickel-Strunz 10th (pending) edition ID: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
Dana 8th edition ID:42.4.1.1

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

20 : Arsenates (also arsenates with phosphate, but without other anions)
8 : Arsenates of Mn
mindat.org URL:http://www.mindat.org/min-72.html
Please feel free to link to this page.

Type Occurrence of Akrochordite

Type Locality:Långban, Filipstad, Värmland, Sweden
Year of Discovery:1922
Associated Minerals at type locality:
PyrochroiteHausmanniteBaryte

Physical Properties of Akrochordite

Diaphaneity (Transparency):Translucent
Colour:reddish brown with a yellowish tint
Hardness (Mohs):3½
Cleavage:Distinct/Good
Two perpendicular directions.
Density (measured):3.194 g/cm3

Crystallography of Akrochordite

Crystal System:Monoclinic
Class (H-M):2/m - Prismatic
Space Group:P21/b {P1 1 21/b} {P21/c} {P1 21/c 1} {P21/a}
Cell Parameters:a = 5.682Å, b = 17.627Å, c = 6.832Å
β = 99.5°
Ratio:a:b:c = 0.322 : 1 : 0.388
Unit Cell Volume:V 674.89 ų (Calculated from Unit Cell)
Z:2
Morphology:Forms veruginous (wart-like) or spherical aggregates of minute crystals.

Optical Data of Akrochordite

Type:Biaxial (+)
RI values: nα = 1.672 nβ = 1.676 nγ = 1.683
Maximum Birefringence:δ = 0.011

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:High
Dispersion:relatively strong

Chemical Properties of Akrochordite

Formula:
(Mn
2+
 
,Mg)
 
5
[(OH)
 
2
|AsO
 
4
]
 
2
 · 4H
 
2
O
Essential elements:As, H, Mg, Mn, O
All elements listed in formula:As, H, Mg, Mn, O

Relationship of Akrochordite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
8.DD.05Chenevixite
Cu
 
2
Fe
3+
2
[(OH)
 
2
|AsO
 
4
]
 
2
8.DD.05Luetheite
Cu
 
2
Al
 
2
[(OH)
 
2
|AsO
 
4
]
 
2
8.DD.10Guanacoite
Cu
 
2
Mg
 
2
(Mg
 
0.5
Cu
 
0.5
)[(OH)
 
2
|AsO
 
4
]
 
2
 · 4H
 
2
O
8.DD.15Aheylite
(Fe
2+
 
,Zn)Al
 
6
[(OH)
 
4
|(PO
 
4
)
 
2
]
 
2
 · 4H
 
2
O
8.DD.15Chalcosiderite
Cu(Fe
3+
 
,Al)
 
6
[(OH)
 
4
|(PO
 
4
)
 
2
]
 
2
 · 4H
 
2
O
8.DD.15Faustite
(Zn,Cu)Al
 
6
[(OH)
 
4
|(PO
 
4
)
 
2
]
 
2
 · 4H
 
2
O
8.DD.15Planerite
Al
 
6
[(OH)
 
4
|HPO
 
4
|PO
 
4
]
 
2
 · 4 H
 
2
O
8.DD.15Turquoise
Cu(Al,Fe
3+
 
)
 
6
[(OH)
 
4
|(PO
 
4
)
 
2
]
 
2
 · 4H
 
2
O
8.DD.20Childrenite
(Fe
2+
 
,Mn
2+
 
)Al[(OH)
 
2
|PO
 
4
] · H
 
2
O
8.DD.20Eosphorite
(Mn
2+
 
,Fe
2+
 
)Al[(OH)
 
2
|PO
 
4
] · H
 
2
O
8.DD.20Ernstite
(Mn
2+
 
,Fe
3+
 
)Al[(OH,O)
 
2
|PO
 
4
] · H
 
2
O
Related Minerals - Hey's Index Grouping:

- +
20.8.1Sarkinite
Mn
2+
2
[OH|AsO
 
4
]
20.8.2Eveite
Mn
2+
2
[OH|AsO
 
4
]
20.8.3Arsenoclasite
Mn
2+
5
[(OH)
 
2
|AsO
 
4
]
 
2
20.8.4Flinkite
Mn
2+
2
Mn
3+
 
AsO
 
4
(OH)
 
4
20.8.5Jarosewichite
Mn
 
3
MnAsO
 
4
(OH)
 
6
20.8.6Allactite
Mn
2+
7
(AsO
 
4
)
 
2
(OH)
 
8
20.8.7Krautite
MnHAsO
 
4
·H
 
2
O
20.8.8Synadelphite
Mn
2+
9
[(OH)
 
9
|As
3+
 
O
 
3
|(As
5+
 
O
 
4
)
 
2
] · 2H
 
2
O
20.8.9Sterlinghillite
Mn
 
3
(AsO
 
4
)
 
2
·4H
 
2
O
20.8.10Geigerite
Mn
 
5
[HAsO
 
4
|AsO
 
4
]
 
2
 · 10H
 
2
O
20.8.12Manganohörnesite
(Mn,Mg)
 
3
(AsO
 
4
)
 
2
·8H
 
2
O
20.8.13Fluckite
CaMnH
 
2
(AsO
 
4
)
 
2
·2H
 
2
O
20.8.14Brandtite
Ca
 
2
(Mn
2+
 
,Mg)[AsO
 
4
]
 
2
 · 2H
 
2
O
20.8.15Parabrandtite
Ca
 
2
Mn
2+
 
[AsO
 
4
]
 
2
 · 2H
 
2
O
20.8.16Wallkilldellite-(Mn)
Ca
 
2
Mn
2+
3
[(OH)
 
2
|AsO
 
4
]
 
2
 · 9H
 
2
O
20.8.17Berzeliite
NaCa
 
2
(Mg,Mn
2+
 
)
 
2
[AsO
 
4
]
 
3
20.8.18Manganberzeliite
(Ca,Na)
 
3
(Mn
2+
 
,Mg)
 
2
[AsO
 
4
]
 
3
20.8.19Magnesiochlorophoenicite
(Mg,Mn)
 
3
Zn
 
2
(AsO
 
4
)(OH,O)
 
6
20.8.20Villyaellenite
(Mn,Ca,Zn)
 
5
(AsO
 
3
OH)
 
2
(AsO
 
4
)
 
2
·4H
 
2
O
20.8.21Hematolite
(Mn,Mg,Al)
 
15
(AsO
 
3
)(AsO
 
4
)
 
2
(OH)
 
23
20.8.22Grischunite
NaCa
 
2
Mn
2+
5
Fe
3+
 
[AsO
 
4
]
 
6
 · 2H
 
2
O

Other Names for Akrochordite

Synonyms:
AchrochorditeAcrochordite
Other Languages:
German:Achrochordit
Acrochordit
Akrochordit
Russian:Акрохордит
Spanish:Achrochordita
Acrochordita
Akrochordita

Other Information

Other Information:Readily soluble in dilute H2SO4, yielding a purple (lilac) solution.
Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Akrochordite

Reference List:Flink (1922) Geologiska Föeningens I Stockholm. Förhandlinger, Stockholm: 44: 773 (as Acrochordite).

Almström (1923) Geologiska Föeningens I Stockholm. Förhandlinger, Stockholm: 45: 117.

American Mineralogist (1923): 8: 167.

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.

American Mineralogist (1968): 53: 1779.

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.

Internet Links for Akrochordite

Search Engines:
  • Look for Akrochordite on Google
  • Look for Akrochordite images on Google
    • External Links:
  • Look for Akrochordite on Webmineral
  • Look for Akrochordite on Athena Mineralogy
  • Look for Akrochordite on Wikipedia
  • Look for Akrochordite on Mineralien Atlas
  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Akrochordite in the Natural History Museum (London) online catalogue
  • Akrochordite details from Handbook of Mineralogy (PDF)
    • Mineral Dealers:
  • Wendel Minerals - Auktion & Shop
  • Buy minerals from Mineralium.com
  • Lapis Mineral Magazin
  • Fabre Minerals - search for Akrochordite specimens
  • Find Akrochordite on www.crystalclassics.co.uk
  • SpiriferMinerals.com - high quality specimens
  • Edwards Minerals - Fine Specimens
  • Buy from David K Joyce minerals
  • Buy Fine Minerals from mineralsweb.com
  • Fine Minerals from Dan Weinrich Minerals
  • The Arkenstone - Fine Minerals
  • DAKOTA MATRIX offers Cabinet and Rare Species from Worldwide Localities.
    • Jobs:
  • Mining & Geology Jobs

    • Page Sponsor

    Sponsorship:This page is currently not sponsored. Click here to sponsor this page.

    Localities for Akrochordite

    Hide Locality List
    The 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. ? 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.
    Sweden
     
    • Värmland
      • Filipstad
    		Geologiska Föeningens 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.
        • Nordmark
    		No reference listed
    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
    Google
     
    www.mindat.org Web
    Copyright © Jolyon Ralph and Ida Chau 1993-2009. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them.Further information contact the Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of hundreds of members and supporters. If you would like to add information to improve the quality of our database, then click here to register. Current server date and time: 6th Nov 2009 18:33:09