sedimentary
Stromatolite
Biogenic Sedimentary Rock (Lithified microbial mat)
Hardness: 3-4 (Mohs scale), Color: Grey, tan, or brownish-grey with distinct concentric or wavy layering, Luster: Dull to earthy, Structure: Layered/Laminated, Composition: Primarily Calcium Carbonate (CaCO3).
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Physical properties
Hardness: 3-4 (Mohs scale), Color: Grey, tan, or brownish-grey with distinct concentric or wavy layering, Luster: Dull to earthy, Structure: Layered/Laminated, Composition: Primarily Calcium Carbonate (CaCO3).
Formation & geological history
Formed by the trapping, binding, and cementation of sedimentary grains by biofilms (microbial mats) of microorganisms, especially cyanobacteria. These are some of the oldest records of life on Earth, dating back over 3.5 billion years.
Uses & applications
Primarily used for geological research and education. Polished specimens are sold to collectors or used in decorative lapidary arts and jewelry.
Geological facts
Stromatolites are responsible for the first oxygen on Earth through photosynthesis. While most are ancient fossils, living stromatolites can still be found today in places like Shark Bay, Australia.
Field identification & locations
Look for distinctive, repetitive fine layers that may be flat, domed, or columnar. They are often found in limestone or dolomite formations. A key field identification is the presence of 'cabbage-like' or wavy banding that doesn't follow standard inorganic sedimentation patterns.
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