Portlandite | |
---|---|
![]() Portlandite and ettringite | |
General | |
Category | Oxide mineral |
Formula (repeating unit) | Ca(OH)2 |
IMA symbol | Por[1] |
Strunz classification | 4.FE.05 |
Dana classification | 06.02.01.04 Brucite group |
Crystal system | Trigonal |
Crystal class | Hexagonal scalenohedral (3m) H-M symbol: (3 2/m) |
Space group | P3m1 |
Unit cell | a = 3.589 Å, c = 4.911 Å; Z = 1 |
Identification | |
Color | Colorless, white to greenish white |
Crystal habit | Hexagonal plates; commonly fibrous, powdery, massive. |
Cleavage | Perfect on {0001} |
Tenacity | Sectile with flexible cleavage plates |
Mohs scale hardness | 2 |
Luster | Pearly on cleavages |
Diaphaneity | Transparent |
Specific gravity | 2.23 |
Optical properties | Uniaxial (−) |
Refractive index | nω = 1.574 nε = 1.547 |
Birefringence | δ = 0.027 |
Solubility | Soluble in water producing an alkaline solution |
Alters to | Alters to CaCO3 on exposure to CO2 bearing waters |
References | [2][3][4][5][6] |
Portlandite is a hydroxide-bearing mineral typically included in the oxide mineral class. It is the naturally occurring form of calcium hydroxide (Ca(OH)2) and the calcium analogue of brucite (Mg(OH)2).