Wood-ash stone in Angophora costata (Gaertn.) J.Britt. following Sydney bushfires

Summary

Wood-ash stone, consisting of lumps of carbonate several cubic centimetres in size, were found in the burnt portion of a stump and a trunk (burnt on the ground) of a common Sydney sandstone tree, Angophora costata, following the 2002 new-year fires in the Lane Cove valley. It appears to result from the fusion and crystallisation of the ash at temperatures <1000°C. The study material is composed mostly of calcite, as determined by X-ray diffraction and petrological analysis, and in comparison to other examples it contains higher concentrations of Ca and Mg but much lower levels of K, Na and P. This composition probably accounts for the absence of rare potassium carbonates that are reported in other studies. This is the second known occurrence of wood-ash stone in Australia and outside North America.

Keywords:

• wood ash
• mineralization
• chemical composition
• forest fires
• trees
• burning
• Angophora costata