Niedermayrite is a rare hydrated copper cadmium sulfate hydroxide mineral with formula: Cu<sub>4</sub>Cd(SO<sub>4</sub>)<sub>2</sub>(OH)<sub>6</sub>÷4H<sub>2</sub>O. It crystallizes in the monoclinic system and occurs as encrustations and well formed vitreous blue-green prismatic crystals. It has a specific gravity of 3.36.
Niedermayrite was named for Gerhard Niedermayr (born 1941), an Austrian mineralogist affiliated with the Naturhistorisches Museum in Vienna, Austria. It was first described in 1998 from a mine in the Lavrion District, Attica, Greece. It is also reported from the Ophir District, Tooele County, Utah. The environment is in brecciated marble. The cadmium dominant analogue of campigliaite.