Found this interesting stone yesterday. It is 3" across, I have found some small triangular pieces about 3/4" long not sure what they are. Someone told me they were pigment stones and when needed some was scraped off to use, don't know.
Well they did like the color red I find plenty of hammers made from red sandstone cobbles. Yours looks to be shaped maybe from grinding meal on it. Any dimples on it? The manos I find are made from red sandstone cobbles to.
Sorry willjo. There are some folks on here who will tell you every slightly chipped or strangely shaped rock you find is a 'genuine Indian artifact', but that ain't the case. If they were paint stones, they will generally be found in a village site, so did you find any other things in the area that you thought might be Indian related? The best thing for your find is 'What would I use this for?,' so see if you can scrape some off and if it is a usable paint.
I guess the two most common paint stones would be hematite for red pigment and graphite for black. But such stones are going to show a surface that has been scraped for the pigment. Your rock, in contrast, does not show it was being scraped. Had it been a paint stone, it would show it had been used that way. Look at the difference with these 2 graphite paint stones. You can see these pieces were scraped and gouged for the graphite, which would then usually be mixed with bear fat, I guess.
Here's another example of a paint stone. A lot of RI Formation shale has pockets of hemetite(ochre) and limonite(yellow pigment). This little shale pebble apparently had a pocket of yellow limonite that was extracted. Found on same camp as the graphite paint stones. It would have already been a broken pebble by the looks of it with a fat pocket of limonite....