Mineral Factbook

Ankerite

Ca(Fe2+,Mg)(CO3)2IMA symbol: Ankgrandfathered

Ankerite is a carbonate or nitrate mineral with the formula Ca(Fe2+,Mg)(CO3)2, crystallizing in the trigonal system. It has a Mohs hardness of 3.6-4.5, typically white, brown, gray or yellow in color, with a silky or vitreous luster, a specific gravity of 3-3.12. Its streak is white.

Photos

Ankerite specimen photo
Hannes Grobe · CC BY-SA 4.0 · Commons
Ankerite specimen photo
Mineralysk · CC BY-SA 4.0 · Commons
Ankerite specimen photo
Mineralysk · CC BY-SA 4.0 · Commons
Ankerite specimen photo
Mineralysk · CC BY-SA 4.0 · Commons

Crystallography

Crystal systemtrigonal crystal systemWikidata (CC0)
Space groupR -3 :H
Cell (Å, °)a = 4.824, b = 4.824, c = 16.1217; α = 90, β = 90, γ = 120
Cell volume324.905 ų, Z = 3
Axial ratios1.0000:1:3.3420calculated from COD 9001246
Source structureCOD 9001246 (American Mineralogist, 1989) — 1 of 7 structures

Powder X-ray diffraction (calculated)

2θ (degrees, Cu Kα1)I/I₀ (max 100)
d (Å)2.9011.7952.2011.8152.0222.412
I/I₀10025.521.219.516.814.8

xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9001246; idealized occupancies, no preferred orientation.

Physical properties

Density (calculated)3.091 g/cm³calculated from COD 9001246
Hardness (Mohs)
3.6-4.5single sourceFord, Dana's Textbook of Mineralogy, 3rd ed. (1922)
Specific gravity
3-3.12 g/cm3corroboratedFord, Dana's Textbook of Mineralogy, 3rd ed. (1922)
Color
brown, gray, white, yellowsingle sourceFord, Dana's Textbook of Mineralogy, 3rd ed. (1922)
Streak
whitesingle sourceWikidata (CC0)
Luster
silky, vitreoussingle sourceFord, Dana's Textbook of Mineralogy, 3rd ed. (1922)

Classification

Nickel-Strunz (10th)5.AB.10Wikidata (CC0)
Nickel-Strunz (9th)5.AB.10Wikidata (CC0)
Dana (8th)14.2.1.2Wikidata (CC0)