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Ankerite

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Regia mine, Bellmunt del Priorat, Priorat, Tarragona, Catalonia, Spain
© David Soler

Show Ankerite Photos (85)
Formula:
Ca(Fe
2+
 
 ,Mg,Mn
2+
 
)(CO
 
3
)
 
2
System:TrigonalColour:Brown, white to grey, ...
Lustre:Vitreous, PearlyHardness:3½ - 4
Name:Named after Mathias J. Anker (1771-1843), Styrian (Austria) mineralogist.


Dolomite Group. Ankerite-Dolomite Series, and the Ankerite-Kutnohorite Series.

Most (unanalysed) Ankerite specimens are usually Fe-bearing (ferroan) Dolomite (Mg>Fe).

Classification of Ankerite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:5/B.03-20
Nickel-Strunz 10th (pending) edition ID:5.AB.10

5 : CARBONATES (NITRATES)
A : Carbonates without additional anions, without H2O
B : Alkali-earth (and other M2+) carbonates
Dana 7th edition ID:14.2.1.2
Dana 8th edition ID:14.2.1.2

14 : ANHYDROUS NORMAL CARBONATES
2 : AB(XO3)2
Hey's CIM Ref.:11.13.6

11 : Carbonates
13 : Carbonates of Fe
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Type Occurrence of Ankerite

Type Locality:Styrian Erzberg, Eisenerz, Styria, Austria
Year of Discovery:1825

Occurrences of Ankerite

Geological Setting:Low grade metamorphism of ironstones and banded iron formation.

Physical Properties of Ankerite

Lustre:Vitreous, Pearly
Diaphaneity (Transparency):Transparent, Translucent
Colour:Brown, white to grey, yellowish-brown, tan.
Streak:White
Hardness (Mohs):3½ - 4
Tenacity:Brittle
Cleavage:Perfect
Perfect on {1011}
Fracture:Sub-Conchoidal
Density (measured):2.93 - 3.1 g/cm3
Density (calculated):3.11 g/cm3

Crystallography of Ankerite

Crystal System:Trigonal
Class (H-M):3 - Rhombohedral
Space Group:R3
Cell Parameters:a = 4.8312(2) Å, c = 16.1663(3) Å
Ratio:a:c = 1 : 3.346
Unit Cell Volume:V 326.78 ų (Calculated from Unit Cell)
Z:3
Morphology:Crystals commonly rhombohedral with {1011} or, less commonly, {4041} dominant.
Twinning:Simple twins on {0001}, {1010}. {1120}
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data: Peaks:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Ankerite

Type:Uniaxial (-)
RI values: nω = 1.690 - 1.750 nε = 1.510 - 1.548
Maximum Birefringence:δ = 0.180 - 0.202

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

Chemical Properties of Ankerite

Formula:
Ca(Fe
2+
 
 ,Mg,Mn
2+
 
)(CO
 
3
)
 
2
Essential elements:C, Ca, Fe, O
All elements listed in formula:C, Ca, Fe, Mg, Mn, O
Common Impurities:Ce,La,TR

Relationship of Ankerite to other Species

Series:Forms a series with Dolomite (see here)
Forms a series with Kutnohorite (see here)
Related to:
  • Dolomite Group
    • Related Minerals - Nickel-Strunz Grouping):
    5.AB.05Calcite
    Ca(CO
     
    3
    		)
    5.AB.05Gaspéite
    (Ni,Mg,Fe)CO
     
    3
    5.AB.05Magnesite
    MgCO
     
    3
    5.AB.05Otavite
    CdCO
     
    3
    5.AB.05Rhodochrosite
    MnCO
     
    3
    5.AB.05Siderite
    FeCO
     
    3
    5.AB.05Smithsonite
    ZnCO
     
    3
    5.AB.05Spherocobaltite
    CoCO
     
    3
    5.AB.10Dolomite
    CaMg(CO
     
    3
    		)
     
    2
    5.AB.10Kutnohorite
    Ca(Mn,Mg,Fe)(CO
     
    3
    		)
     
    2
    5.AB.10Minrecordite
    CaZn(CO
     
    3
    		)
     
    2
    5.AB.15Aragonite
    CaCO
     
    3
    5.AB.15Cerussite
    PbCO
     
    3
    5.AB.15Strontianite
    SrCO
     
    3
    5.AB.15Witherite
    BaCO
     
    3
    5.AB.20Vaterite
    CaCO
     
    3
    5.AB.25Huntite
    CaMg
     
    3
    		[CO
     
    3
    		]
     
    4
    5.AB.30Norsethite
    BaMg(CO
     
    3
    		)
     
    2
    5.AB.35Alstonite
    BaCa(CO
     
    3
    		)
     
    2
    5.AB.40Olekminskite
    Sr(Sr,Ba)(CO
     
    3
    		)
     
    2
    5.AB.40Paralstonite
    BaCa(CO
     
    3
    		)
     
    2
    5.AB.45Barytocalcite
    BaCa(CO
     
    3
    		)
     
    2
    5.AB.50Carbocernaite
    (Ca,Na)(Sr,Ce,Ba)(CO
     
    3
    		)
     
    2
    5.AB.55Benstonite
    (Ba,Sr)
     
    6
    		(Ca,Mn)
     
    6
    		Mg(CO
     
    3
    		)
     
    13
    5.AB.60Juangodoyite
    Na
     
    2
    		Cu(CO
     
    3
    		)
     
    2
    Related Minerals - Hey's Index Grouping:
    11.13.1Siderite
    FeCO
     
    3
    11.13.2Pyroaurite
    Mg
     
    6
    		Fe
    3+
    2
    		[(OH)
     
    16
    		|CO
     
    3
    		] · 4H
     
    2
    		O
    11.13.3Sjögrenite
    Mg
     
    6
    		Fe
    3+
    2
    		[(OH)
     
    16
    		|CO
     
    3
    		] · 4H
     
    2
    		O
    11.13.4Brugnatellite
    Mg
     
    6
    		Fe
    3+
     
    		[(OH)
     
    13
    		|CO
     
    3
    		] · 4H
     
    2
    		O
    11.13.5Coalingite
    Mg
     
    10
    		Fe
    3+
    2
    		[(OH)
     
    24
    		|CO
     
    3
    		] · 2H
     
    2
    		O
    Related Minerals - Dana Grouping):
    14.2.1.1Dolomite
    CaMg(CO
     
    3
    		)
     
    2

    Other Names for Ankerite

    Synonyms:
    Tautoklin
    German names:
    AnkeritEisendolomit
    Russian names:
    Анкерит
    Spanish names:
    Ankerita
    Varieties:
    Manganous AnkeriteNickeliferous Ankerite

    Other Information

    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 Ankerite

    Reference List:Rocza (1926) Zentralblatt Mineralien: 229.

    Winchell (1927), part 2: 75.

    Larsen, E.S. and Berman, H. (1934) The Microscopic Determination of the Nonopaque Minerals, Second edition, USGS Bulletin 848: 229.

    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: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 208-217.

    Goldsmith, J.R., D.L. Graf, J. Witters & D.A. Northrop (1962), Studies in the system CaCO3•MgCO3•FeCO3: (1) Phase relations; (2) A method for major element spectrochemical analyses; and, (3) Composition of some ferroan dolomites. Journal of Geology: 70: 659-688.

    Tschermaks Mineralogische und Petrographische Mitteilungen: 24: 279-286.

    Walmsley, J.C. and Lang, A.R. (1992a) On submicrometer inclusions in diamond coat: Crystallography and composition of ankerites and related rhombohedral carbonates. Mineralogical Magazine: 56: 533-543.

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    Localities for Ankerite

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