Fig. 2
From: Recent progress in instrumental techniques for architectural heritage materials
OM photographs. a Quartz aggregates and a ceramic fragment; b newly formed volcanic ash material at a quartz grain/binder interface; c shrinkage cracks caused by dehydration within the binder groundmass; d shell materials as important substances of the aggregate particles; e plane-polarized light micrography of dendritic black crust; f cross-polarized light micrography of dendritic black crust; g external form of the patina in plane-polarized light mode; h discontinuous patina in plane-polarized light mode [55, 61, 62], copyright (2005, 2007) Elsevier and (2011) Springer Link