Portlandite
- Named portlandite because it is a common product of hydration of portland cement
- Formula: Ca(OH)2
- Space group: P-3m1 (No. 164)
- Crystal system: trigonal
- Crystal class: -3 2/m
- Lattice parameters: a = b = 3.5918 Å, c = 4.9063 Å, α = β = 90°, γ = 120°
Picture (public domain): SEM image of fractured hardened cement paste, showing plates of calcium hydroxide and needles of ettringite
Crystal structure (click on the picture to download the VESTA file):
(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)
- CaO6 octahedra (blue)
- Oxygen (red)
- Hydrogen (white)
For a 3D interactive version on sketchfab, see here:
The Fascination of Crystals and Symmetry 