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Ankerite

A valid IMA mineral species - grandfathered
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About AnkeriteHide

05106670017271921065409.jpg
Matthias Joseph Anker
Formula:
Ca(Fe2+,Mg)(CO3)2
Usually contains large amounts of Mg and sometimes Mn.
Colour:
Brown, white to grey, yellowish-brown, tan, fawn, greenish
Lustre:
Pearly
Hardness:
3½ - 4
Specific Gravity:
2.93 - 3.10
Crystal System:
Trigonal
Member of:
Name:
Named after Matthias Joseph Anker (1771-1843), Austrian mineralogist. Originally considered to be Ca(Mg,Fe)(CO3)2 (eg. Hey, 1955, with >10% FeCO3) with no specific requirement for Fe>Mg, before being redefined as strictly having Fe>Mg, i.e. with the dominant endmember CaFe(CO3)2. It was commonly given the end-member formula Ca2FeMg(CO3)4; Hey (1955) actually used the name ferrodolomite for CaFe(CO3)2. The redefinition of the name means the majority of old specimens labelled "ankerite" are now considered to be ferroan dolomite, and true ankerite is quite rare.
Dolomite Group. Ankerite-Dolomite Series, and the Ankerite-Kutnohorite Series.

Note: Most (unanalysed) "ankerite" specimens are actually Fe-bearing (ferroan) dolomite (Mg>Fe), because of nomenclature changes. The majority of alleged "ankerite" photos here actually depict Fe-rich dolomite (except for a relatively few analytically confirmed ankerites). Even the old so-called "type locality ankerite" from Erzberg, Styria, would not quite fit the modern definition, with analysis showing Mg0.520Fe0.457Mn0.021 apfu (Schoklitsch, 1935 - taken from the Deer-Howie-Zussmann textbook).

The end-member composition CaFe(CO3)2 with dolomitic structural ordering has neither been synthesized (Goldsmith et al., 1962; Rosenberg, 1967) nor has it been found in nature (Dana's System of Mineralogy, Vol. II, 1951; Deer et al., 1962; Goldsmith et al., 1962; Beran, 1975); compositions reach about 70 mol.% CaFe(CO3)2. Chai and Navrotsky (1996), who synthesised disordered ankerite under high-pressure-high-temperature conditions, considered ordered CaFe(CO3)2 to be non-existent.


Unique IdentifiersHide

Mindat ID:
239
Long-form identifier:
mindat:1:1:239:6

Similar NamesHide

IMA Classification of AnkeriteHide

Approved, 'Grandfathered' (first described prior to 1959)

Classification of AnkeriteHide

5.AB.10

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

14 : ANHYDROUS NORMAL CARBONATES
2 : AB(XO3)2
11.13.6

11 : Carbonates
13 : Carbonates of Fe

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.

SymbolSourceReference for Standard
AnkIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43
AnkKretz (1983)Kretz, R. (1983) Symbols of rock-forming minerals. American Mineralogist, 68, 277–279.
AnkSiivolam & Schmid (2007)Siivolam, J. and Schmid, R. (2007) Recommendations by the IUGS Subcommission on the Systematics of Metamorphic Rocks: List of mineral abbreviations. Web-version 01.02.07. IUGS Commission on the Systematics in Petrology. download
AnkWhitney & Evans (2010)Whitney, D.L. and Evans, B.W. (2010) Abbreviations for names of rock-forming minerals. American Mineralogist, 95, 185–187 doi:10.2138/am.2010.3371
AnkThe Canadian Mineralogist (2019)The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download
AnkWarr (2020)Warr, L.N. (2020) Recommended abbreviations for the names of clay minerals and associated phases. Clay Minerals, 55, 261–264 doi:10.1180/clm.2020.30

Physical Properties of AnkeriteHide

Pearly
Transparency:
Translucent
Colour:
Brown, white to grey, yellowish-brown, tan, fawn, greenish
Streak:
White
Hardness:
3½ - 4 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
Perfect on {1011}
Fracture:
Hackly
Density:
2.93 - 3.10 g/cm3 (Measured)    3.11 g/cm3 (Calculated)
Comment:
density 3.121 for type location material (Ford, 1971)

Optical Data of AnkeriteHide

Type:
Uniaxial (-)
RI values:
nω = 1.69 - 1.75 nε = 1.51 - 1.548
Max. Birefringence:
δ = 0.180 - 0.202
Based on recorded range of RI values above.

Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.

Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.

Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars.

Surface Relief:
Moderate
Dispersion:
Strong

Chemistry of AnkeriteHide

Mindat Formula:
Ca(Fe2+,Mg)(CO3)2

Usually contains large amounts of Mg and sometimes Mn.
Element Weights:
Element% weight
O44.455 %
Fe25.861 %
Ca18.560 %
C11.124 %

Calculated from ideal end-member formula.
Common Impurities:
Mn

Chemical AnalysisHide

Crystallography of AnkeriteHide

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 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}
Comment:
For sample with 68 mol% CaFe(CO3)2 (Reeder & Dollase, 1989). A sample with ca. 70 mol% CaFe(CO3)2 has a = 4.836 and 16.186 A (Ross & Reeder, 1992).

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0015665AnkeriteBeran A, Zemann J (1977) Refinement and comparison of the crystal structures of a dolomite and of an Fe-rich ankerite Tschermaks Mineralogische und Petrographische Mitteilungen 24 279-2861977Erzberg, Etage Dreikonig, Styria, Austria0293
0001449AnkeriteRoss N L, Reeder R J (1992) High-pressure structural study of dolomite and ankerite American Mineralogist 77 412-421Image19920293
0001274AnkeriteReeder R J, Dollase W A (1989) Structural variation in the dolomite-ankerite solid-solution series: An X-ray, Mossbauer, and TEM study sample AMNH 8059 American Mineralogist 74 1159-1167Image19890293
0001273AnkeriteReeder R J, Dollase W A (1989) Structural variation in the dolomite-ankerite solid-solution series: An X-ray, Mossbauer, and TEM study sample AMNH 6376 American Mineralogist 74 1159-1167Image19890293
0001450AnkeriteRoss N L, Reeder R J (1992) High-pressure structural study of dolomite and ankerite American Mineralogist 77 412-421Image19921.9293
0001451AnkeriteRoss N L, Reeder R J (1992) High-pressure structural study of dolomite and ankerite American Mineralogist 77 412-421Image19922.97293
0001452AnkeriteRoss N L, Reeder R J (1992) High-pressure structural study of dolomite and ankerite American Mineralogist 77 412-421Image19924293
CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

Loading XRD data...
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
d-spacingIntensity
2.899 Å(100)
1.812 Å(6)
2.199 Å(6)
Comments:
Data from Webmineral, but may not be true ankerite. When Fe>Mg the main(104) peak must be at least 2.910, and even more if you have significant Mn and other substitutions.

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Stage 3b: Earth’s earliest hydrosphere>4.45
17 : Marine authigenic Hadean minerals (see also #24)
Near-surface Processes
23 : Subaerial aqueous alteration by non-redox-sensitive fluids (see also #47)
25 : Evaporites (prebiotic)
High-? alteration and/or metamorphism
31 : Thermally altered carbonate, phosphate, and iron formations
Stage 4b: Highly evolved igneous rocks>3.0
35 : Ultra-alkali and agpaitic igneous rocks
36 : Carbonatites, kimberlites, and related igneous rocks
Stage 5: Initiation of plate tectonics<3.5-2.5
40 : Regional metamorphism (greenschist, amphibolite, granulite facies)
Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere<0.6
50 : Coal and/or oil shale minerals<0.36
Stage 10b: Anthropogenic minerals<10 Ka
54 : Coal and other mine fire minerals (see also #51 and #56)
Geological Setting:
Low-grade metamorphism of ironstones and banded iron formation. Carbonatites and other carbonate-rich alkaline igneous rocks.

Synonyms of AnkeriteHide

Other Language Names for AnkeriteHide

Catalan:Ankerita
Dutch:Ankeriet
French:Ankérite
Hungarian:Ankerit
Italian:Ankerite
Lithuanian:Ankeritas
Norwegian:Ankeritt
Polish:Ankeryt
Portuguese:Ankerite
Simplified Chinese:铁白云石
Slovak:Ankerit
Spanish:Ankerita
Swedish:Ankerit
Ukrainian:Анкерит

Varieties of AnkeriteHide

Manganese-bearing AnkeriteA manganese-bearing variety of ankerite.
Nickel-bearing AnkeriteA nickel-bearing variety of ankerite.
TautoklinGreyish-white variety of ankerite.

Relationship of Ankerite to other SpeciesHide

Member of:
Other Members of Dolomite Group:
DolomiteCaMg(CO3)2Trig. 3 : R3
KutnohoriteCaMn2+(CO3)2Trig. 3 : R3
MinrecorditeCaZn(CO3)2Trig. 3 : R3
NorsethiteBaMg(CO3)2Trig. 3 2 : R3 2
ŠkáchaiteCaCo(CO3)2Trig. 3 : R3
'Unnamed (Pb analogue of Dolomite)'PbMg(CO3)2
Forms a series with:

Common AssociatesHide

Associations Based on Photo Data:
446 photos of Ankerite associated with QuartzSiO2
205 photos of Ankerite associated with CalciteCaCO3
156 photos of Ankerite associated with SphaleriteZnS
141 photos of Ankerite associated with ChalcopyriteCuFeS2
125 photos of Ankerite associated with FluoriteCaF2
122 photos of Ankerite associated with GalenaPbS
103 photos of Ankerite associated with PyriteFeS2
77 photos of Ankerite associated with GoethiteFe3+O(OH)
63 photos of Ankerite associated with SideriteFeCO3
61 photos of Ankerite associated with MetacinnabarHgS

Related Minerals - Strunz-mindat GroupingHide

5.AB.05SideriteFeCO3Trig. 3m (3 2/m) : R3c
5.AB.05RhodochrositeMnCO3Trig. 3m (3 2/m) : R3c
5.AB.05CalciteCaCO3Trig. 3m (3 2/m) : R3c
5.AB.05SmithsoniteZnCO3Trig. 3m (3 2/m) : R3c
5.AB.05GaspéiteNiCO3Trig. 3m (3 2/m) : R3c
5.AB.05SpherocobaltiteCoCO3Trig. 3m (3 2/m) : R3c
5.AB.05MagnesiteMgCO3Trig. 3m (3 2/m) : R3c
5.AB.05OtaviteCdCO3Trig. 3m (3 2/m) : R3c
5.AB.05 va'Parakutnohorite'
5.AB.10DolomiteCaMg(CO3)2Trig. 3 : R3
5.AB.10MinrecorditeCaZn(CO3)2Trig. 3 : R3
5.AB.10ŠkáchaiteCaCo(CO3)2Trig. 3 : R3
5.AB.10KutnohoriteCaMn2+(CO3)2Trig. 3 : R3
5.AB.15AragoniteCaCO3Orth. mmm (2/m 2/m 2/m)
5.AB.15CerussitePbCO3Orth. mmm (2/m 2/m 2/m)
5.AB.15WitheriteBaCO3Orth. mmm (2/m 2/m 2/m)
5.AB.15StrontianiteSrCO3Orth. mmm (2/m 2/m 2/m)
5.AB.20VateriteCaCO3Hex. 6/mmm (6/m 2/m 2/m) : P63/mmc
5.AB.25HuntiteCaMg3(CO3)4Trig. 3 2 : R3 2
5.AB.30NorsethiteBaMg(CO3)2Trig. 3 2 : R3 2
5.AB.35AlstoniteBaCa(CO3)2Tric.
5.AB.40ParalstoniteBaCa(CO3)2Trig. 3 2 : P3 2 1
5.AB.40OlekminskiteSr(Sr,Ca,Ba)(CO3)2Trig. 3 2 : P3 2 1
5.AB.45BarytocalciteBaCa(CO3)2Mon. 2/m : P21/m
5.AB.50Carbocernaite(Ca,Na)(Sr,Ce,Ba)(CO3)2Orth. mm2
5.AB.55BenstoniteBa6Ca6Mg(CO3)13Trig. 3 : R3
5.AB.60JuangodoyiteNa2Cu(CO3)2Mon. 2/m : P21/b

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Ankerite in petrologyHide

Internet Links for AnkeriteHide

References for AnkeriteHide

Reference List:

Localities for AnkeriteHide

Showing 4,231 localities.

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the Image symbol to view information about a locality. The Image symbol next to localities in the list can be used to jump to that position on the map.
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