Metal in a rock?

[OldScout]

I found this at the river yesterday. I can't figure out what these bumps in the rock are. They are very un-characteristic for rocks here. Actually have never seen anything else in the rivers I search like it. They are in the rock. Please see photos. The irregularities are about the size of a penny each. Bumpy. The bumps should have easily eroded in this river.

 

[mamabear]

I have found hematite that conformed to the rock it was on & then it was covered with that same rock. Looks like the kind u have in your pic. I am trying to find the piece so you can see what it looks like.

 

[OldScout]

Thanks. I would like to see your sample if you get a chance. The inclusions here do not appear to be magnetic.

 

[DDancer]

Inclusions like the ones shown are usually concentrations of other minerals that formed as the host rock formed. What you have appears to be pretty high in silicates but I cant tell if its vitrified sandstone or a form of quartzite though the layering is suggestive of a sedimentary formation. The nodules maybe some form of ferrous mineral, like hematite, that formed just prior to being locked into the host rock. I'm just guessing because of the reddish coloration however the nobby look of the nodules might also be chalcedony nodules that were forming when the host rock set around them.