[Fionnbharr (finn:-)]

Grant Sarver would tell you he makes the bits for jack hammers, and demolition hammers from 1085. Which can be had from old sections of railroad track, if you can find it legally, and work it... Agricultural steels tend to run from 1065-1095, and heatreated and tempered prooperly they would work well too. 5160 Coil spring would work to, again if you tempered back enough. Scrap demolition hammer bits if you have a scrapyard that sells them, or if you can buy them from a rental company would also work well... Jack hammer bits have an air supply hole through center, and shouldn't be used in a hot forge after being used as a struck tool, and with mushrooming heads and such there is always a schrapnel risk. Most S series steels would do fine too (the S is for shock resistant I believe>)

Whatever you end up using you should use a differential heat treat on it. By which I mean forge it to shape and then anneal or normalize as best you can, then harden just the working end, and temper. It is also recommended to use a Soft steel hammer. This is the safest combination, and will deliver the most energy to the stone.

So, do you want to buy new steel and are you looking for a shopping list? Or are you going to be scrapings, and just plann on using whatever is handy that will do the job???