THE ETTRINGITE GROUP OF MINERALS
The Ettringite Group
is composed of hydrated calcium sulfate hydroxide minerals with a common trigonal
It is named for its most common member, ettringite
, which is actually a rather uncommon mineral.
The general formula for this group is Ca6
The X can be either aluminum, chromium, iron, manganese or silicon.
ion group can be partially replaced by the rare B(OH)4
ion group as in a couple of the members of this group sturmanite
ion group can also be partially replaced by carbonate ions as in thaumasite
, these types of substitutions are minimal.
is sometimes classified as a silicate
because of its silicon content, but it lacks the SiO4
tetrahedrons required for inclusion in that class.