sedimentary
Stromatolite
Laminated biogenic sedimentary structure (formed by Cyanobacteria)
Hardness: 3-5 (Mohs scale), Color: Brown, grey, tan, and earthy tones, Luster: Dull to earthy, Structure: Layered or laminated 'microbial mats', Cleavage: None (conchoidal or irregular fracture), Specific Gravity: 2.6-2.8
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Physical properties
Hardness: 3-5 (Mohs scale), Color: Brown, grey, tan, and earthy tones, Luster: Dull to earthy, Structure: Layered or laminated 'microbial mats', Cleavage: None (conchoidal or irregular fracture), Specific Gravity: 2.6-2.8
Formation & geological history
Formed by the trapping, binding, and cementation of sedimentary grains by biofilms of microorganisms, specifically cyanobacteria. They represent some of the earliest life forms on Earth, dating back over 3.5 billion years.
Uses & applications
Used primarily as decorative specimens for collectors, jewelry (when cabochon-cut), and in educational settings to demonstrate the origin of life and evolution of the atmosphere.
Geological facts
Stromatolites were responsible for the 'Great Oxygenation Event' that created Earth's oxygen-rich atmosphere. They are considered 'living fossils' as they still form today in hypersaline lagoons like Shark Bay, Australia.
Field identification & locations
Identify by a distinctive 'wavy' or 'concentric' laminated pattern resembling tree rings or stacked pancakes. Common in Precambrian rock formations globally. Collectors should look for preserved internal lamination layers.
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