Pickeringite
![](/Images/godic/202502/02/Pickeringite-873534140.jpg")
![Pickeringite in the Natural History Museum](/Images/godic/202502/02/Pickeringite4140.jpg")
Pickeringite is a magnesium aluminium sulfate mineral with formula MgAl2(SO4)4·22(H2O). It forms a series with halotrichite.
It forms as an alteration product of pyrite in aluminium rich rocks and in coal seams. It also occurs in pyrite rich hydrothermal ore deposits in arid regions. It forms in fumaroles and in caves. It occurs with kalinite, alunogen, epsomite, melanterite, copiapite and gypsum.