sedimentary
Stromatolite
Cyanobacteria fossilized formation (CaCO3)
Hardness: 4-5 (Mohs), Color: banded shades of brown, gray, and tan, Luster: dull to earthy, Structure: laminated/layered accretionary structure, Specific Gravity: 2.6-2.8
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Physical properties
Hardness: 4-5 (Mohs), Color: banded shades of brown, gray, and tan, Luster: dull to earthy, Structure: laminated/layered accretionary structure, Specific Gravity: 2.6-2.8
Formation & geological history
Produced by the activity of cyanobacteria (blue-green algae) which trap and bind sediment into layers. These are some of the oldest records of life on Earth, dating back over 3.5 billion years.
Uses & applications
Scientific research on early life, decorative lapidary work, jewelry (especially cabochons), and geological collecting.
Geological facts
Stromatolites are responsible for oxygenating the early Earth's atmosphere through photosynthesis. While rare today, living colonies still exist in places like Shark Bay, Australia.
Field identification & locations
Identify by characteristic concentric or planar wavy laminae (layers). Found in ancient limestone or dolomite beds globally. Collectors look for high-contrast banding.
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