I've given some thought to trying the old bronze-antler-iron tools. You could also use other rocks, espcially to create a lighter background (as was done by the American Indians among others, including those who lived around here).

Just for information: you can shatter stone by heating it in a fire and then, when it's very, very hot dashing cold water on it -- but stand somewhere safe if you do it. I do not recommend this method, but I've seen it done and it can be spectacular (and dangerous).

HuwG, I'm sorry that I was misleading. When I said "igneous" I meant the products of vulcanism, the rocks that abound around here in the malpais. This was and is a seismicly active area, with hot springs, cooled lava flows, and historic vulcanism. Yellowstone Park is about three hours away by road, as is Craters of the Moon National Park. There was quite an earthquake in 1983, and there was the Teton dam collapse some years before that. At work, in the library, everything over 48 inches high must either have an oversized base or be securely fastened to the walls. As I said, this area rocks.