Calcite crystals, starch grains aggregates or... POCC? Comment on 'calcite crystals inside archaeologial plant tissues'
Résumé
The microscopic objects presented by F.O. Freitas and P.S. Martins as ‘recrystallized calcite crystals’ and ‘starch grain aggregates’ are both compound crystals, end products of the transformation of plant calcium oxalate crystals into calcite in wood fires. These calcareous silty particles are the major component of the wood ashes familiar to archaeologists. Petrographic microscope remains the more efficient tool for this kind of research.