A usually rounded or columnar sedimentary structure consisting of alternating layers of carbonate or silicate sediment and fossilized microbial mats, produced over geologic time by the trapping, binding, or precipitating of minerals by groups of microorganisms, primarily cyanobacteria.
stro·mat′o·litic (-măt′l-ĭtĭk) adj.
(click for a larger image)stromatolite
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.