The mineral woodruffite, Zn2+x/2 (Mn4+1-x Mn3+x O2·yH2O, x ∼ 0.4 and y ∼ 0.7, is the first known example of a new type of Mn oxide characterized by large tunnels that measure 3 and 4 octahedra (6.9 × 9.2 Å on a side. These tunnels are rectangular in cross-section and are the largest of any yet reported in natural or synthetic Mn oxides. The thermal stability of woodruffite is comparable to that of todorokite and other large-tunnel Mn oxide phases, breaking down at ∼300 °C and eventually transforming to a spinel-type structure. The woodruffite structure may serve as a model for a new class of octahedral molecular sieves with enhanced capabilities as catalysts and selective cation-exchange agents.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology