Stromatolite
Image: James St. John (jsj1771) <a rel="nofollow" class="external free" href="https://www.flickr.com/people/jsjgeology/">https://www.flickr.com/people/jsjgeology/</a> (CC BY 2.0)
Mineral NameStromatolite
Chemical FormulaCaCO3
Mohs Hardness7
Crystal Systemamorphous
Lusterdull
Streak Colorwhite
CleavageNone, as it is a rock structure
Fractureconchoidal
Specific Gravity2.65
Colorsbrown, grey, tan, dark brown
Transparencyopaque
Type LocalityFort Laclede Bed, Laney Member, Green River Formation, southwestern Wyoming, USA
Mineral GroupCarbonates
Usesscientific study, collector specimens, decorative stone
Associated Mineralscalcite, dolomite, quartz, chert, clay minerals
Raritycommon
Description
This is a cross-sectional slice of a fossilized stromatolite, revealing intricate, wavy, and concentric layers in shades of dark brown, grey, and tan. The structure exhibits a fan-like or domed growth pattern, characteristic of microbial mat accretion.
Geological Context
Stromatolites are ancient biogenic sedimentary structures formed by the trapping and binding of sediment particles by microbial mats, primarily cyanobacteria, in shallow aquatic environments. This specimen from the Eocene Green River Formation represents a fossilized microbial community from ancient Lake Gosuite.
