Fig. 7: Archeological sample BB1b after 49-day VHT.

a Photograph of pre-reaction coupon with stainless steel wire for suspension in VHT apparatus (scale bar is 1000 µm), (b) photograph of sample surface after reaction (scale bar is 100 µm), (c) SEM image of a cross section through BB1b (scale bar is 100 µm), (d) higher magnification SEM image of area in red box in (c). EDS maps (shown below) showing distribution of major elements present at the surface in (d).