Dark gray flint or chert fragment
Microcrystalline quartz (SiO₂), commonly with minor chalcedony and impurities
Category
Browse organic structure (not a rock) specimens identified by the Rock Identifier community.
Dark gray flint or chert fragment
Microcrystalline quartz (SiO₂), commonly with minor chalcedony and impurities
Fossilized Shark Tooth
Chondrichthyes tooth
Petrified Wood
Silicified Wood (Quartzo-feldspathic fossil wood)
Geode (Unopened)
Silica-rich concretion (SiO2)
Fossilized Bone
Permineralized Bone (Vertebrate Fossil)
Chert (Flint)
Microcrystalline Quartz (SiO2)
Tahitian black pearl strand
Cultured pearl; aragonite (CaCO₃) nacre
Petrified Wood
Silicified Wood (primarily Chalcedony/Quartz, SiO2)
Chert / Flint
Chert (Microcrystalline Quartz, SiO2)
Sandstone with Iron Staining
Clastic sedimentary rock (primarily SiO2 with Fe2O3 staining)
Banded Chert / Agate
Silicon Dioxide (SiO2)
Granite / Feldspar gravel
Granite (felsic intrusive igneous rock)
Chert (Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Geode (unopened)
Chert / Chalcedony Geode (SiO2)
Quartz Geode
Silicon Dioxide (SiO2)
Sandstone (Weathered Coastal Boulder)
Arenite (composed primarily of SiO2)
Chert (variations include Flint or Jasper)
Cryptocrystalline Quartz (SiO2)
Chert (Flint nodule)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Fossiliferous Limestone
Calcium carbonate (CaCO3) with fossil inclusions
Lapis Lazuli
Lapis Lazuli (A complex rock primarily composed of Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)
Amber
Succinicum (C10H16O)
Petrified Wood
Silicified Wood (Silicon Dioxide - SiO2)
Chert (Flint)
Chert (SiO2)
Fossil Shark Tooth
Selachii (fossilized dentition)
Chert (Flint/Jasper variety)
Silicon Dioxide (SiO2)
Petrified Wood
Silicified Wood (SiO2)
Chert (Chert Nodule with Chalky Cortex)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Amber
Succinite (C10H16O)
Jasper
Silicon Dioxide (SiO2) microcrystalline quartz
Coral Fossil (Petrified Coral)
Scleractinia (Order) - Calcified Fossil Skeleton (CaCO3)
Sandstone (with potential fossil inclusions)
Clastic sedimentary rock (primarily SiO2)
Bivalve seashell
Calcareous shell, primarily aragonite (CaCO₃); likely a modern cockle or related bivalve
Chert (Chalcedony/Flint)
Silicon Dioxide (SiO2)
Limestone (Fossiliferous)
Calcium Carbonate (CaCO3)
Jasper (specifically Polychrome or Desert Jasper)
Silicon Dioxide (SiO2) with iron oxide and other mineral impurities
Chert (Flint Pebbles)
Microcrystalline Quartz (SiO2)
Bivalve Fossil in Sedimentary Matrix
Fossiliferous Mudstone (Class: Bivalvia)
Quartz pebble or seed/crumb
SiO2 (if quartz)
Green Chert
Microcrystalline Quartz (SiO2)
Pyritic Mudstone
Argillaceous rock (FeS2)
Bituminous Coal
Coal (Organically derived sedimentary rock)
Shark Tooth Fossil
Chondrichthyes fossil