I bought a set of these ($20) just to try them,, WOW!!, they truly are amazing,,,
7PCS 9/16'' Plug Wedge and Feather Shims Concrete Rock Stone Splitter Hand Tool 711221674764 | eBay
The wedges can split rocks with amazing ease,,, The holes only need to be deep enough to get the wedge in,,, 9/16" diameter holes,, IIRC,,,
Drill the row of holes, insert the feathers and wedges,,,
tap each wedge in sequence,, repeat the hitting,, repeat the hitting.
You do not even need to strike the wedge very hard,,,
Success!! :thumbsup: