Fig. 7

BSE images performed on selected samples: a general appearance of a ceramic with small grain size (sample 319). Note the same orientation of phyllosilicates and fissures; b general appearance of a ceramic characterized by coarse quartz grains with angular morphology (sample 328); c detailed image in which a phyllosilicate enriched in iron can be seen (sample 323). The phyllosilicate shows separation along basal planes due to dehydroxylation. The white arrow indicates the presence of a small rutile crystal; d detailed image of a calcite crystal with polygonal pores mainly located along the cleavage planes (sample 334); e presence of an ellipsoidal pore that suggests the previous existence of carbonatic shell (sample 329). The brighter border indicates a reaction between carbonate and the matrix; f detailed image of a reaction rim observed in Fig. 7e: quartz grains with smoothed edges and newly-formed calcium silicates (see inset with EDS spectra); g clays sheets mould around harder quartz grain. A brighter Fe-rich framboid can be seen (sample 332); h development of secondary porosity in the matrix (sample 347), with micrometric rounded to elongated pores