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Ecdemite

Big Photo

Harstigen Mine, Pajsberg, Filipstad, Värmland, Sweden
© Kjell Gatedal

Show Ecdemite Photos (6)
Formula:
Pb
 
6
[As
 
2
O
 
7
|Cl
 
4
]
System:TetragonalColour:Greenish-yellow, yellow
Lustre:Vitreous, GreasyHardness:2½ - 3
Name:From the Greek for unusual, in allusion to the composition.
Dimorph of:Heliophyllite


Apparently dimorphous with Heliophyllite.

Classification of Ecdemite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:3/D.10-100
Nickel-Strunz 10th (pending) edition ID:3.DC.65

3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
C : With Pb (As,Sb,Bi), without Cu
Dana 8th edition ID:46.2.1.1

46 : ANTIMONITES AND ARSENITES CONTAINING HYDROXYL OR HALOGEN
2 : Miscellaneous
Hey's CIM Ref.:23.7

23 : Arsenites
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Type Occurrence of Ecdemite

Type Locality:Långban, Filipstad, Värmland, Sweden
Year of Discovery:1877
Geological Setting of type material:Metamorphosed Fe-Mn ore body.
Associated Minerals at type locality:
Manganoan CalciteMagnetiteLeadHeliophylliteFreedite
FinnemaniteCopperAndradite

Physical Properties of Ecdemite

Lustre:Vitreous, Greasy
Diaphaneity (Transparency):Translucent
Comment:Lustre vitreous on cleavages and greasy on fractures
Colour:Greenish-yellow, yellow
Streak:Light yellow
Hardness (Mohs):2½ - 3
Cleavage:Distinct/Good
On {001}, distinct.
Density (measured):7.14 g/cm3
Density (calculated):7.3 g/cm3

Crystallography of Ecdemite

Crystal System:Tetragonal
Cell Parameters:a = 10.82Å, c = 25.6Å
Ratio:a:c = 1 : 2.366
Unit Cell Volume:V 2,997.05 ų (Calculated from Unit Cell)
Z:8
Morphology:Crystals small tabular and in foliated masses.

Optical Data of Ecdemite

Type:Uniaxial (-)
RI values: nω = 2.320 nε = 2.250
Maximum Birefringence:δ = 0.070

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

Chemical Properties of Ecdemite

Formula:
Pb
 
6
[As
 
2
O
 
7
|Cl
 
4
]
Essential elements:As, Cl, O, Pb
All elements listed in formula:As, Cl, O, Pb

Relationship of Ecdemite to other Species

Related Minerals - Nickel-Strunz Grouping):
3.DC.05Laurionite
PbClOH
3.DC.05Paralaurionite
PbClOH
3.DC.10Fiedlerite
Pb
 
3
Cl
 
4
F(OH)·H
 
2
O
3.DC.15Penfieldite
Pb
 
2
[OH|Cl
 
3
]
3.DC.20Laurelite
Pb(F,Cl,OH)
 
2
3.DC.25Bismoclite
BiOCl
3.DC.25Daubréeite
BiO(OH,Cl)
3.DC.25Matlockite
PbFCl
3.DC.25Rorisite
CaFCl
3.DC.25Zavaritskite
BiOF
3.DC.25Zhangpeishanite
BaFCl
3.DC.30Nadorite
PbSb[O
 
2
|Cl]
3.DC.30Perite
PbBi[O
 
2
|Cl]
3.DC.35Aravaipaite
Pb
 
3
[F
 
3
|AlF
 
6
] · H
 
2
O
3.DC.35Calcioaravaipaite
PbCa
 
2
[(F,OH)
 
3
|AlF
 
6
] · H
 
2
O
3.DC.40Thorikosite
Pb
 
3
[OH|(SbO
 
3
,AsO
 
3
)|Cl
 
2
]
3.DC.45Mereheadite
Pb
 
2
[O|OH|Cl]
3.DC.50Blixite
Pb
 
2
[(O,OH)
 
2
|Cl]
3.DC.55Pinalite
Pb
 
3
WO
 
3
Cl
 
2
3.DC.60Symesite
Pb
 
10
[O
 
7
|SO
 
4
|Cl
 
4
] · H
 
2
O
3.DC.65Heliophyllite
Pb
 
3
AsO
 
4-n
Cl
 
2n+1
3.DC.70Mendipite
Pb
 
3
[O
 
2
|Cl
 
2
]
3.DC.75Damaraite
Pb
 
3
[O
 
2
|OH|Cl]
3.DC.80Onoratoite
Sb
 
8
O
 
11
Cl
 
2
3.DC.85Cotunnite
PbCl
 
2
3.DC.90Pseudocotunnite
K
 
2
PbCl
 
4
3.DC.95Barstowite
Pb
 
4
[Cl
 
6
|CO
 
3
] · H
 
2
O
Related Minerals - Hey's Index Grouping:
23.2Nanlingite
CaMg
 
4
[F
 
2
|AsO
 
3
]
 
2
23.3Leiteite
Zn[As
 
2
O
 
4
]
23.5Kuznetsovite
(Hg-Hg)Hg
2+
 
[Cl|AsO
 
4
]
23.6Paulmooreite
Pb
 
2
[As
 
2
O
 
5
]
23.8Heliophyllite
Pb
 
3
AsO
 
4-n
Cl
 
2n+1
23.9Finnemanite
Pb
 
5
[Cl|(AsO
 
3
)
 
3
]
23.10Gebhardite
Pb
 
8
[O|Cl
 
6
|(As
 
2
O
 
5
)
 
2
]
23.11Zimbabweite
(Na,K)
 
2
PbAs
 
4
(Ta,Nb,Ti)
 
4
O
 
18
23.13Rouseite
Pb
 
2
Mn
2+
 
[AsO
 
3
]
 
2
 · 2H
 
2
O
23.14Freedite
Pb
 
15
(Cu,Fe
2+
 
)
 
3
[O
 
7
|Cl
 
10
|(AsO
 
3
)
 
4
]
23.15Manganarsite
Mn
 
3
[(OH)
 
4
|As
 
2
O
 
4
]
23.17Armangite
Mn
2+
26
[CO
 
3
|(HAsO
 
3
)
 
4
|(AsO
 
3
)
 
14
]
23.18Karibibite
Fe
 
2
As
 
4
O
 
9
23.19Schneiderhöhnite
Fe
2+
 
Fe
3+
3
[As
 
5
O
 
13
]
23.20Lazarenkoite
(Ca,Fe)FeAs
 
3
O
 
7
·3H
 
2
O
23.21Stenhuggarite
CaFeSbO(AsO
 
3
)
 
2
23.22Tomichite
(V,Fe)
 
4
Ti
 
3
AsO
 
13
OH

Other Names for Ecdemite

Synonyms:
Ekdemite
German names:
EcdemitEkdemit
Spanish names:
EcdemitaEkdemita

Other Information

Other Information:Soluble in HNO3 or warm HCl, and in alkalies.
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 Ecdemite

Reference List:Nordenskiöld, A.E. (1877) Geologiska Föeningens I Stockholm. Förhandlinger, Stockholm: 3: 379 (as Ekdemit).

Hamberg (1889) Geologiska Föeningens I Stockholm. Förhandlinger, Stockholm: 11: 229.

Larsen, E.S. (1921) The Microscopic Determination of the Nonopaque Minerals, First edition, USGS Bulletin 679: 71.

Sillén and Melander (1941) Zeitschrift für Kristallographie: 103: 420.

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.: 1036-1037.

Welin, E. (1968) X-ray powder data for minerals from Långban and the related mineral deposits of Central Sweden. Arkiv för Mineralogi och Geologi, Stockholm: 4(30): 499–541.

Internet Links for Ecdemite

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    Localities for Ecdemite

    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.
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    (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.
    Greece
     
    • Attikí (Attica; Attika) Prefecture
      • Lavrion (Laurion; Laurium) District
        • Lavrion District slag localities
          • Passa Limani area
    		Gelaude, Piet, van Kalmthout, Piet, and Rewitzer, Christian (1996) Laurion: The Minerals of the Ancient Slags, Janssen Print, Nijmegen, The Netherlands
          • Sounion area
    		Gelaude, Piet, van Kalmthout, Piet and Rewitzer, Christian, (1996) Laurion: The Minerals in the Ancient Slags, Janssen Print, Nijmegen, The Netherlands
          • Thorikos area
    		Gelaude, Piet, van Kalmthout, Piet and Rewitzer, Christian (1996) Laurion: The Minerals in the Ancient Slags, Janssen Print, Nijmegen, The Netherlands
          • Vrissaki area
    		Gelaude, Piet, van Kalmthout, Piet, and Rewitzer, Christian (1996) Laurion: The Minerals in the Ancient Slags, Janssen Print, Nijmegen, The Netherlands
    Italy
     
    • Tuscany
      • Livorno Province
        • Piombino
    		Muenchener Micromounter-Lithothek
    Sweden
     
    • Värmland
      • Filipstad
    		Geologiska Föeningens I Stockholm. Förhandlinger, Stockholm (1877) 3, 379; 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: 1036; 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.
        • Pajsberg
    		GFF 125 (2003) 2, 87-98; 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: 1036.
    No reference listed
    USA
     
    • California
      • Inyo Co.
        • Surprise Valley District
    Mineral and/or Locality
    Google
     
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