Coal
Bituminous Coal / Anthracite
Category
Browse organic materia (not a rock or mineral) specimens identified by the Rock Identifier community.
Coal
Bituminous Coal / Anthracite
Chert (Jasper/Flint variety)
Silicon Dioxide (SiO2)
Banded Chert
Silicon Dioxide (SiO2)
Chert (Smooth River Pebble)
Microcrystalline or cryptocrystalline Quartz (SiO2)
Polished banded agate (likely picture jasper or petrified wood)
Microcrystalline quartz, SiO₂, with iron-oxide and clay inclusions
Chert (Jasper/Flint variety)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Yellow Chert
Microcrystalline Quartz (SiO2)
Fossilized Wood / Petrified Wood
Petrified Wood (Silicified Flora)
Limestone
Calcium carbonate (CaCO3)
Pearl
Calcium Carbonate (CaCO3) with Conchiolin
Grey Chert River Pebble
Microcrystalline Quartz (SiO2)
Chert
Microcrystalline Quartz (SiO2)
Graphite
Graphite (Carbon, C)
Chert (Jasper type)
Microcrystalline Quartz (SiO2)
Glauconitic Sandstone
Glauconitic arenite (contains (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2)
Silty Shale or Mudstone
Siltstone/Mudstone (Clastic Sedimentary Rock)
Limestone
Calcium Carbonate (CaCO3) / Limestone
Banded Chert
Microcrystalline Quartz (SiO2)
Petrified Wood
Silicified Wood (primarily SiO2 - Silicon Dioxide / Chalcedony)
Chert (Jasper/Chalcedony Pebble)
Silicon Dioxide (SiO2)
Fossil Shell Fragment (possibly Brachiopod or Bivalve)
Calcium Carbonate (CaCO3) - Phylum Brachiopoda or Mollusca
Petrified Wood
Silicified Wood (SiO2)
Fossiliferous Limestone
Carbonate Sedimentary Rock (primarily CaCO3)
Banded Chert
Silicon Dioxide (SiO2)
Chert (Nodular)
Chert (SiO2 - Microcrystalline Quartz)
Weathered iron-rich rock, likely ferruginous sandstone or lateritic concretion
Iron-oxide–cemented sandstone; commonly dominated by quartz (SiO₂), goethite (FeO(OH)) and hematite (Fe₂O₃)
Pearl
Nacre (aragonite, CaCO₃, in an organic conchiolin matrix)
Chert (specifically Jasper/Flint)
Microcrystalline Quartz (SiO2)
Chert (and Flint)
Cryptocrystalline Quartz (SiO2)
Chert (Iron-stained)
Microcrystalline Quartz (SiO2)
Fossilized Shell in Limestone
Carbonate sedimentary rock with Bivalvia or Brachiopoda remains
Limestone
Calcium Carbonate (CaCO3)
Fossiliferous Limestone (Crinoid stem fragment)
Crinoidea (Phylum Echinodermata) in Calcite matrix
Chert (variations include Flint or Jasper)
Silicon Dioxide (SiO2)
Chert / Chalcedony Nodules
Microcrystalline Quartz (SiO2)
Jasper
Microcrystalline Quartz (SiO2)
Chert (Jasper/Agate mix)
Microcrystalline Quartz (SiO2)
Chert (Jasper variety)
Silicon Dioxide (SiO2)
Amber
Succinite (C10H16O)
Yellow Chert
Sedimentary cryptocrystalline quartz (SiO2)
Weathered iron-rich limestone or sandstone
Ferruginous carbonate/siliciclastic rock; likely calcite- and iron-oxide-bearing matrix
Limestone
Calcareous sedimentary rock (CaCO3)