Secondary names

Calcium iron magnesium carbonate; Ca-Fe-Mg carbonate; Brown Spar

IMA Code

Ank

	Formula	Name	Family	Number min-max	Isotope mole fraction	State	Relevance
	$Ca$	Calcium	element	1 - 1.2		constituent element	main
	$Fe^{2+}$	Iron(II) cation	element	0.4 - 0.7		constituent element	main
	$Mg$	Magnesium	element	0.25 - 0.4		constituent element	main
	$Mn^{2+}$	Manganese(II) cation	element	0 - 0.15		constituent element	main
	$(CO_3)^{2-}$	Carbonate anion	chemical function	2		anionic radical	main

Composition comments

with $Fe \gt Mg$ - Typical chemical formula: $CaFe^{2+}_{0.6}Mg_{0.35}Mn^{2+}_{0.05}(CO_3)_2$

Chemical functions

	Function	Number
	$(CO_3)^{2-}$	2

Chemical bonds

	Bond	Number
	$\cdot Ca^{2+} \cdot O^{-}-$	1
	$\cdot Fe^{2+} \cdot O^{-}-$
	$\cdot Mg^{2+} \cdot O^{-}-$
	$\cdot Mn^{2+} \cdot O^{-}-$
	$\dddot - \dddot - C \dddot - O^{-2/3}$	3

Oxides

Formula	$CaO$	$FeO$	$MgO$	$MnO$	$CO_{2}$
Mass fraction (%)	27.17	20.89	6.84	1.72	42.65

Oxides comments

oxydes composition corresponding to the typical chemical formula

Strunz

Class

carbonates - nitrates (05)

Division

carbonates without additional anions, without H2O (05.A)

Family

Alkali-earth (and other M2+) carbonates (05.AB)

Code

05.AB.10

Dana

Major class

carbonates, nitrates, borates (V)

Class

anhydrous carbonates (14)

Type

with compound formula A+B++(CO3)2 (14.02)

Group

Dolomite group (Trigonal: R-3) (14.02.01)

Code

14.02.01.02

Phase type

crystalline

Crystal system

trigonal

Crystal class

rhombohedral

Crystal class symbol

-3 (S6)

Crystal spacegroup

R-3

Refringence type

uniaxial

Refringence sign

negative

Birefringence

0.18 - 0.20

Refraction index $n_o$ (w)

1.69 - 1.75

Refraction index $n_e$ (e)

1.51 - 1.55

Pure color

white

Color

brown, brownish yellow, gray, gray brown, greenish, white

Diaphaneity

translucent to subtranslucent

Luster

vitreous

Links

• Webmineral: Ankerite
• Mindat: Ankerite
• Wikipedia: Ankerite
• Handbook of Mineralogy (Min. Soc. Am): Ankerite