looking at faience (e.g., mummy beads) and ceramic mediums using EDX and SEM methods, among others. The microstructure of faience is significantly different than that of clays / ceramics and also somewhat different that that of glass. The differences between faience and glass are not as marked as those between faience and various clays. My lab work over the past 2 decades fully supports Jamey's foregoing points. There are also a variety of frits similar to faience; however, their differences are subtle (though distinct) in nature - at least from a microstructure standpoint. Hope that this helps as oppose to creating confusion for anyone.
Thanks.
Austin