Latin stromat-, stroma bed covering + English -o- + -lite
First Known Use: 1930
Layered deposit, mainly of limestone, formed by the growth of blue-green algae (seecyanobacteria). These structures are usually characterized by thin, alternating light and dark layers that may be flat, hummocky, or dome-shaped. Stromatolites were common in Precambrian time (more than 543 million years ago). Some of the first forms of life on Earth are recorded in stromatolites in rocks 3.5 billion years old. Stromatolites continue to form in certain areas today, most abundantly in Shark Bay in western Australia.