Some Stromatolytes:

Certain fossil Stromatolytes are considered some of the oldest known fossils of life on Earth. The ones pictured here are 'only' about half a
billion years old though.....

A Stromatolyte fossil.

At least 3 Stromatolyte fossils. Closer view, inset.

Close-up of another Stromy. I will give no location on these, since there are those who would scavenge or vandalize them.