The sandy texture, color, and look makes me immediately think of concrete.

Hi,

Been busy cheering my grandson on to a state championship in 7-8 year old coaches pitch base ball.  Wendell won!!!

And in my spare time, I've decided my guess on this is it's quartzite in transition.  I read about fossillierous sandstone and  quartzose sandstone and mudstone and siltstone and decided it was sorta like those but not quite.  So I found this Wikipedia statement that sounded right:

"When sandstone is cemented to quartzite, the individual quartz grains recrystallize along with the former cementing material to form an interlocking mosaic of quartz crystals. Most or all of the original texture and sedimentary structures of the sandstone are erased by the metamorphism."

I'll post a pic of the tiny tiny, I mean very tiny, quartz crystals visible on the edge of the rock.  These crystals line the outside edge of the rock in multiple rows - but you have to look very closely - or bring a magnifying glass - to see them.  I don't know what's on the inside and don't want to break it open to find out else I destroy its million year transition.  I think I'll keep it like it is...

What do you think?  Quartzite?

Cheers,
r

Great detective work, Robert! Well done.
It's near about impossible to find a picture that matches what you're looking for.

The last pic of your piece, if I got it right, the one showing the vug
in the side of your piece, looks like you can almost see some gray-to-white banding, or layers
that start to look like agate. But that's another form of quartz, too.

Just guessing, but I'm seeing an old fine clay layer full of rounded pebbles
and other gravel in the bottom of a creek,
and then along comes an event that pushes and squeezes
that layer of clay and the whole creek together,
compacting it and at the same time heating it enough for all the silica to melt and permeate the layer and fill any cracks,
making the whole thing hard as rock!
And that would probably be my guess if I held it my hand.
Best guess and I'm sticking with it!

Keep up the good work!