Saponite is a trioctahedral mineral of the smectite group. Its chemical formula is Ca_0.25(Mg,Fe)₃((Si,Al)₄O₁₀)(OH)₂·n(H₂O). It is soluble in sulfuric acid. It was first described in 1840 by von Svanberg. Varieties of saponite are griffithite, bowlingite and sobotkite.