A monoclinic mineral, Pb₁₆(AsO₄)₄Cl₁₄(OH)₆or Pb₁₆(AsO₄)₄Cl₁₄O₂(OH)₂; forms stubby tablets; sp gr, 7.1; associated with laurionite, matlockite, and fiedlerite on altered slags at Laurium, Greece.