So I'm aiming to visit some of the Altamira Shale (Monterey Formation Shale) exposures in my city and try to find some fossils in fallen shale pieces. However, I simply cannot find a good way to split shale (I also have small rocks of Altamira Shale in my backyard, which could be seen as a sort of "practice"). The shale that I get are usually very hard and compact, as seems to not crack very easily with the materials I have. I don't have a real chisel, but I makeshift them (nail, screws, and screwdrivers). When I use them, it seems to just dig a hole in the area where I'm striking at and creates no cracks. Does anyone who has experience with Monterey Shale know the best way to split a shale like this, preferably clean in half?
(It seems that the rocks I'm trying to split are the exact same rocks found in any other part of the Monterey Formation, like Jalama Beach)