Need this crystal identfied

Ok so when I bought this crystal they told me what kind it was and I was going to do research on it and forgot what it was called can anyone refresh my memory please. I had such a unique name and it started with an S but that is all I know

Stromatolite stone

You have these to thank for your existence.

\m/ Kat

Thanks thor that is the one

ya so i figured when I bought it she said that it that they are the oldest things on this earth