Portlandite
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Portlandite is a hydroxide-bearing mineral typically included in the oxide mineral class. It is the naturally occurring form of calcium hydroxide and the calcium analogue of brucite.
Portlandite and ettringite
Ettringite
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Ettringite is a hydrous calcium aluminium sulfate mineral with formula: Ca6Al2312·26H2O. It is a colorless to yellow mineral crystallizing in the trigonal system. The prismatic crystals are typically
Portlandite
…as large crystals and masses. It occurs in association with afwillite, calcite, larnite, spurrite, halite, brownmillerite, hydrocalumite, mayenite and ettringite. It was first described in 1933 for an occurrence at Scawt Hill, Larne, County Antrim, Northern Ireland. It was named portlandite because the chemical…
Ettringite, Kalahari manganese fields, Northern Cape Province, South Africa
Ettringite, 6.5 × 3.2 cm. N'Chwaning Mines, Kalahari manganese fields, Northern Cape Province, South Africa
SEM image of fractured hardened cement paste, showing thin hexagonal plates of portlandite (calcium hydroxide) and needles of ettringite (micron scale)
Fibroradiated ettringite needles on slag (Concordia smelter, Eschweiler, Aachen, Germany)