This is the hammer used to split and trim stratified rocks or dig into sediments. Its chisel end is handy for splitting shale layers in search of fossils. It's also well suited for carving clean exposures of sediment layers like varved clays or lake beds to prepare them for sampling or photography. The hammer head is suitable for light chisel work. This hammer must not be used as a chisel, that is, by hammering on the hammer's face, or it may chip. All rock hammers should be used wearing eye protection, because chips from rocks or from the hammer can fly in all directions. Proper chisels are made of softer metal. For paleontologists or workers in sedimentary rock country, this may be the only rock hammer needed.
This is an Estwing hammer, which is widely available. Its chisel end is also very handy for gardening, especially if you aren't a bricklayer.