Sauconite is a complex phyllosilicate mineral of the smectite 0.3Zn )2·4H2O. It forms soft earthy bluish white to red-brown monoclinic crystals typically massive to micaceous in habit. It has a Mohs hardness of 2.45. Optically it is biaxial positive with refractive index values of nα = 1.550 - 1.580, nβ = 1.590 - 1.620 and nγ = 1.590 - 1.620. and seams in the oxidized zones of zinc deposits. It occurs in association with hemimorphite , chrysocolla and various iron oxides.
It was named for the Saucon Valley in Pennsylvania