fossil

Stromatolite

Biogenic sedimentary structure (Stromatolite)

Hardness: Varies depending on mineral replacement, typically 3 to 4 on Mohs scale for calcite/limestone; Color: Grey, brown, tan, or white with distinct concentric laminae and banded or layered internal growth structures; Luster: Dull to vitreous;…

Luster: Dull to vitreous

Identified July 28, 2026More fossil →

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Physical properties

Formation & geological history

Formed by the trapping, binding, and cementation of sedimentary grains by micro-organisms, principally cyanobacteria (blue-green algae), in shallow marine or freshwater environments. Some of the oldest known fossils on Earth, dating back over 3.5 billion years.

Uses & applications

Used primarily as educational specimens, in geological research regarding the early history of life and oxygenation of Earth's atmosphere, and as decorative display or lapidary pieces for fossil collectors.

Geological facts

Stromatolites are responsible for producing the oxygen in Earth's atmosphere through photosynthesis over billions of years, paving the way for complex multicellular life. Living stromatolites can still be found in extreme environments today, such as Shark Bay in Western Australia.

Field identification & locations

Can be identified in the field by their distinctive domed, columnar, or branching layered structures visible in cross-section within limestone or chert formations. Common locations include ancient marine sedimentary deposits worldwide.

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