I started to post that suggestion, but there are just too many lines that “could” be grooved and they are very course, in a similar way the rest of the stone is. No difference in texture from wear.
Here is an axe head / mall or hammer whatever you would like to call it. I'm not an expert either but this rock came out of the creek and its groove is not smoothe but it has a slick finish. It's heavy over 3.5lb. I found the rock above in a near by old gravel rd. Most people wouldn't look there for artifacts but in the past people used creek gravel to make their roads better as they did in this old rd. I'm sure the above rock came from the same creek. If the above rock was formed by water the grooves would be slick and smoothe from the water passing over it, also the groove is very symetrical and the groove continues around the backside. I have found grinding tools in this area that seem to be made out of the same kind of rock. Strangely, I rarely find points in this area so I think they may have grown a lot of there food. I think they may have attached a stick to the above rock to furrow their gardens.
Not necessarily. The walls & floor of the Grand Canyon aren't slick and smooth, and water has been forming it for 5 million years.
