Stromatolite - a microbial reef resulting from the activity of cyanobacteria or blue-green algae. They form in both desalinated and salt water. The name comes from the Greek "layered stone". Stromatolites are formed as a result of the trapping and binding of marine sediments, and also as a result of the mineral fixation of microbial communities. Used as an ornamental stone.
You can see stromatolite stone for sale and buy it in the Minerals of Russia online store.