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Ankerite

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Matthias Joseph Anker
Formula:
Ca(Fe2+,Mg)(CO3)2
Usually contains minor Mg and/or Mn.
System:
Trigonal
Colour:
Brown, white to grey, ...
Lustre:
Vitreous, Pearly
Hardness:
3½ - 4
Member of:
Name:
Named after Mathias J. Anker (1771-1843), Styrian (Austria) mineralogist.
Dolomite Group. Ankerite-Dolomite Series, and the Ankerite-Kutnohorite Series.

Note: Most (unanalysed) "ankerite" specimens are usually Fe-bearing (ferroan) dolomite (Mg>Fe).

Crystals of the composition CaFe(CO3)2 have neither been synthesized (Goldsmith et al., 1962; Rosenberg, 1967) nor have they been found in nature (Dana's System of Mineralogy, Vol. II, 1951; Deer et al., 1962; Goldsmith et al., 1962; Beran, 1975).

Classification of Ankerite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
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
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First Recorded Occurrence of Ankerite

Year of Discovery:
1825

Occurrences of Ankerite

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

Physical Properties of Ankerite

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:
2.93 - 3.1 g/cm3 (Measured)    3.11 g/cm3 (Calculated)

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}
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).
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
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
Max Birefringence:
δ = 0.180 - 0.202
Image 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(Fe2+,Mg)(CO3)2

Usually contains minor Mg and/or Mn.
Essential elements:
All elements listed in formula:
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)
Member of:
Other Members of Group:
DolomiteCaMg(CO3)2
KutnohoriteCa(Mn,Mg,Fe)(CO3)2
MinrecorditeCaZn(CO3)2
NorsethiteBaMg(CO3)2
5.AB.05CalciteCaCO3
5.AB.05Gaspéite(Ni,Mg,Fe)CO3
5.AB.05MagnesiteMgCO3
5.AB.05OtaviteCdCO3
5.AB.05RhodochrositeMnCO3
5.AB.05SideriteFeCO3
5.AB.05SmithsoniteZnCO3
5.AB.05SpherocobaltiteCoCO3
5.AB.10DolomiteCaMg(CO3)2
5.AB.10KutnohoriteCa(Mn,Mg,Fe)(CO3)2
5.AB.10MinrecorditeCaZn(CO3)2
5.AB.15AragoniteCaCO3
5.AB.15CerussitePbCO3
5.AB.15StrontianiteSrCO3
5.AB.15WitheriteBaCO3
5.AB.20VateriteCaCO3
5.AB.25HuntiteCaMg3(CO3)4
5.AB.30NorsethiteBaMg(CO3)2
5.AB.35AlstoniteBaCa(CO3)2
5.AB.40OlekminskiteSr(Sr,Ca,Ba)(CO3)2
5.AB.40ParalstoniteBaCa(CO3)2
5.AB.45BarytocalciteBaCa(CO3)2
5.AB.50Carbocernaite(Ca,Na)(Sr,Ce,Ba)(CO3)2
5.AB.55Benstonite(Ba,Sr)6(Ca,Mn)6Mg(CO3)13
5.AB.60JuangodoyiteNa2Cu(CO3)2
11.13.1SideriteFeCO3
11.13.2PyroauriteMg6Fe23+(OH)16[CO3] · 4H2O
11.13.3Pyroaurite-2HMg6Fe23+(CO3)(OH)16 · 4H2O
11.13.4BrugnatelliteMg6Fe3+(CO3)(OH)13 · 4H2O
11.13.5CoalingiteMg10Fe23+(OH)24[CO3] · 2H2O

Other Names for Ankerite

Name in Other Languages:
Catalan:Ankerita
Dutch:Ankeriet
French:Ankérite
Hungarian:Ankerit
Italian:Ankerite
Lithuanian:Ankeritas
Polish:Ankeryt
Simplified Chinese:铁白云石
Slovak:Ankerit
Spanish:Ankerita
Swedish:Ankerit
Ukrainian:Анкерит

Other Information

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 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.

Reeder, R., Dollase, W. (1989): Structural variation in the dolomite-ankerite solid-solution series: An X-ray, Mössbauer, and TEM study. Am. Mineral. 74, 1159-1167.

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

Ross, N. L. & Reeder, R. (1992): High-pressure structural study of dolomite and ankerite. American Mineralogist, 77, 412-421.

Internet Links for Ankerite

Localities for Ankerite

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.
Mineral and/or Locality  
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