[Thibodeaux]

Pick. The chisel hammer is a brick mason’s tool

[tacticalogic]

That's true, but I've seen both advertised as geologist's hammers. I grew up in a body shop, and have always been partial to metalworker's pick hammers.

[Smokin' Joe]

Yes, the chisel point hammer was first a brick mason's tool, and was adapted to geological use.

The pick style is known among geologists as a "hard rock" hammer--used on igneous and metamorphic rock, while the chisel style is called a "soft rock" hammer and primarily used on sedimentary rock.

Either can be used on either, obviously, but they each tend to perform better in those lithologies because of the structure of the rock.