sedimentary
Stromatolite
Biogenic Sedimentary Rock (composed predominantly of CaCO3)
Hardness: 3-4 (Mohs scale), Color: tan, yellow, grey, and brown banding, Luster: dull to earthy, Crystal Structure: microcrystalline (biogenic layers), Cleavage: none, Specific Gravity: 2.5-2.8
Identified More sedimentary →
Explore Stromatolite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3-4 (Mohs scale), Color: tan, yellow, grey, and brown banding, Luster: dull to earthy, Crystal Structure: microcrystalline (biogenic layers), Cleavage: none, Specific Gravity: 2.5-2.8
Formation & geological history
Formed by the layering of microbial mats, specifically cyanobacteria, which trap and bind sedimentary grains. These date back billions of years (Archean to present), representing some of the oldest records of life on Earth.
Uses & applications
Used as decorative stones, in jewelry (cabochons), as educational specimens in museums, and for geological research to study early Earth environments.
Geological facts
Stromatolites provided the oxygen in Earth's atmosphere through photosynthesis. While most are fossils, living stromatolites can still be found today in places like Shark Bay, Australia.
Field identification & locations
Identified by characteristic wavy or concentric laminar patterns (calcified microbiol mats). Commonly found in ancient marine limestone formations. Collectors should look for distinct, repetitive organic banding.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary