Ankerite
Mineral Ca(Fe,Mg,Mn)(CO3)2
About it
Saddle-shaped rhombs like dolomite but rich in iron, turning yellow-brown as they weather. Common in gold-quartz veins and ironstones; Erzberg, Austria, is a classic source.
- Type
- Mineral
- Group
- Carbonate, dolomite group
- Formula
- Ca(Fe,Mg,Mn)(CO3)2
- Hardness (Mohs)
- 3.5–4
- Specific gravity
- 2.93–3.1
- Streak
- white
- Lustre
- vitreous (glassy), pearly
- Crystal system
- Trigonal
- Colours
- white, buff, yellow-brown, brown, grey
- Transparency
- translucent, transparent
- Cleavage and fracture
- perfect rhombohedral
Typical values: real specimens vary. For more, see mindat.org.