Ettringite
Mineral Ca6Al2(SO4)3(OH)12·26H2O
About it
Lemon-yellow hexagonal prisms from the N’Chwaning mines in South Africa are the collector’s ettringite; it was named for Ettringen in Germany. It also forms as cement and concrete set.
- Type
- Mineral
- Group
- Sulfate, ettringite group
- Formula
- Ca6Al2(SO4)3(OH)12·26H2O
- Hardness (Mohs)
- 2–2.5
- Specific gravity
- 1.77–1.79
- Streak
- white
- Lustre
- vitreous (glassy)
- Crystal system
- Trigonal
- Colours
- colourless, white, pale yellow, lemon yellow
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect prismatic
Typical values: real specimens vary. For more, see mindat.org.