Mutinaite is the third new zeolite from Ferrar dolerites at Mt. Adamson (Northern Victoria Land, Antarctica). The mineral occurs as subspherical aggregates of tiny radiating lath-like fibres or as aggregates of transparent, colourless to pale-milky, tiny tabular crystals; it has vitreous luster, white streak and good {100} cleavage. Mutinaite is brittle with dmeas = 2.14(3) and dcalc = 2.17 g/cm3. Optically, it is biaxial negative with α = 1.485(2), β = 1.487(2) and γ = 1.488(2). The orientation is X = b, Y = a, Z = c. Mutinaite is orthorhombic with a = 20.223(7), b = 20.052(8), c = 13.491(5)Å, space group Pnma. The strongest powder X-ray diffraction lines are (d(Å), I, hkl): 11.20, 84, 101, 011; 9.98, 35, 200,020; 3.85, 100, 501, 051; 3.75, 98, 303; 3.67, 27, 133; 3.00, 32, 503. The framework topology is that of the synthetic zeolite ZSM-5. The chemical formula is: (Na2.76K0.11Mg0.21Ca3.78)∑ = 6.86(Al11.20Si84.91)∑ = 96.11O192 · 60H2O. The Si/Al ratio, equal to 7.6, is the highest found in a natural zeolite. Thermal stability and rehydration capacity are very high. The name is from Mutina, the ancient Latin name of the city of Modena.