Whilst the spectra do not show explicitly that the surface is vitrified, the composition is that of a glaze. It has a different makeup to the limestone body. This means it is very likely that the glaze was made from a ceramic paste applied to the limestone surface. This is clear from the comparison with the ancient glazed ceramic pottery shards.
The microscope photos above of the surface do not show the amorphous state of the layer. This can be shown explicitly by electron microscopic analysis. Further analysis needs to be carried out to confirm the state of the layer. The different chemical composition makes it very unlikely that these surfaces were created by polishing. The layer has the composition, sheen, hardness and glassy texture of a glaze.
Edited by Slave2Fate, 02 January 2013 - 01:19 PM.