Stevensite is a white clay mineral composed of hydrated calcium, sodium and magnesium silicate, with the chemical formula (Ca,Na)<sub>x</sub>Mg<sub>3-x</sub>(Si<sub>4</sub>O<sub>10</sub>)(OH)<sub>2</sub>. The mineral is a member of smectite. The mineral is named after Edwin Augustus Stevens.
Stevensite can be found at the Dean Quarry.