Following my cheapskate thread I've been doing a little more experimenting.
One of the techniques I use when making stone walls, flagstones and the like is to use plaster of paris in a thin shim over a wooden former and then carve out the shape of the stones, flags, sets etc. It's very long winded process but has the advantages of being cheap a 3kg (wow I've just used a French measurement!) sack of Plaster of Paris costs about £2 and the result looks very good.
Well what I tried today was adding various amounts of sand and again dust from the sanding machine to the mix. Sand makes the mix hard to carve when set, (although Mr Dremel with a diamond burr was happy enough) but the results were very good indeed. A sand heavy mixture made good rough cut stone and a dust heavy mix made a good fully finished stone.
Just thought I'd pass it on.