Figure 1. – This is a band contrast image which results from an EBSD run, whereby every pixel has a corresponding EBSD measurement. The grey scale relates to the quality of the data measured – the brighter the area, the better the quality. Zones A-C are progressive overgrowth forms. Zone A is characterised by zoning, which is clearly depicted in CL images. Zone B is a zone of “zero solutions”(i.e., no indexing, which makes it likely that this area is SiO2 but not quartz) and is hence black. In the CL image of this same area, definite overgrowth is displayed that is chalcedony-like in appearance. Zone C is characterised by small, euhedral quartz crystal outgrowths and zone D is porosity, filled with epoxy resin. Transect line 1 relates to Figure 2. The sample has no topography.