Wow that's a weird rock for your area and would be in mine, too. Does it seem softer than chert? Greenstone is much more abradable or workable. Kinda looks like a conglomerate/baybottom but that color is really strange and it has that reddish streak. They sure were using that piece! Figure hammer or even pestle?
It's extreamly hard and dense. Heavy sucker. I agree with hammer or pestel. Only one like it I have found. There was an antler billet close to it. Its harder than the chert. Thinking hammer
OK..back to my topic. I had a thought that it looked a bit like a ballast stone and with the shipwrecks in my area and the role the Ais tribe played during that time I searched only a little and found this from a 1700's spanish wreck site.hmmmm.. very interesting
Here are a couple cobbles I found here in Indiana almost resembling yours. Glacial deposits. Once in a great moon I'd find a chip of this stuff. Then found a couple cobbles, then last year a broken artifact of it in the bottom right. I tried making a point out of it also. Very heavy also.