Although advertised as "clay", these chips seem to be more like a very hard dense plastic. They are at least plastic coated, (possibly like a plasticoat paint). Each chip is not quite as weighty as I thought, although the full set is quite heavy. They are not brightly coloured, and are a little grubby looking, although they are clearly brand new.
Each chip has a plastic sticker in the centre to show its value, and they make a nice satisfying chink when they hit the baize.
They feel quite nice in your hand, and are better than any chips you get in a cheap poker set, but they are definately NOT casino quality. They are worth the money, but I wish I had spent more, and got a 14g set, not 11.5.