The stromatolites?

These "living rocks" were believed to be extinct until 40 years ago. These are actually a type of bacteria that grow on top of each other, growing at the rate of 1mm a year. The ones in this picture are about 1 metre of more tall...
Back in the ancient days these little beasties were responsible for giving off the majority of the oxygen that allowed oxygen breathing life forms to evolve. Hey bud, that's you and me! There is only 1 other place on earth that has these "living rocks" and that is somewhere in Jamaica.