Pearl (Biogenic Mineraloid)
Calcium carbonate (CaCO3) primarily as Aragonite
mineral
Category
Biogenic Material
Browse biogenic material specimens identified by the Rock Identifier community.
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Likely weathered chert or siliceous shale
Cryptocrystalline quartz (SiO₂), possibly with clay minerals
sedimentary
Yellow-brown chert or silicified rock fragment
Microcrystalline quartz (SiO₂), likely chert or chalcedony-rich material
sedimentary
Seashell Fragment (Aragonite/Calcite)
Calcium Carbonate (CaCO3) - Shell fragment
sedimentary
Fossilized Tooth Fragment
Vertebrate Fossil (Mammalia indet.)
fossil
Chert (Flint / Chalcedony pebble)
Silicon Dioxide (SiO2)
sedimentary
Chert
Chert (Microcrystalline Quartz, SiO2)
sedimentary
Pearl
Calcium carbonate (CaCO3) - Aragonite/Calcite variety
mineral
Brown chert or flint pebble
Microcrystalline quartz (SiO₂), commonly with chalcedony and iron-oxide staining
sedimentary
Land Snail Shell
Gastropoda (Calcium Carbonate, CaCO3)
fossil
Pearl
Calcium carbonate (CaCO3) as Aragonite or Calcite
mineral
Freshwater Pearl
Calcium Carbonate (CaCO3) - Aragonite/Calcite organic composite
gemstone
Chert (Pebble)
Microcrystalline Quartz (SiO2)
sedimentary
Pearl
Calcium carbonate (CaCO3) - mainly Aragonite with Conchiolin
mineraloid
Flint (chert), likely brown flint
Microcrystalline quartz/chalcedony (SiO₂)
sedimentary
Weathered iron-rich chert or jasper
Microcrystalline quartz (SiO₂), commonly colored by iron oxides/hydroxides
sedimentary
Fossilized shell or coral fragment
Indeterminate biogenic carbonate; likely calcite/aragonite (CaCO₃)
fossil
Chert (likely chalcedony-rich flint)
Microcrystalline quartz, SiO₂ (quartz/chalcedony)
sedimentary
Ammolite
Biogenic gemstone (Aragonite, CaCO3)
mineral
Chert nodule in sandstone or iron-stained host rock
Microcrystalline quartz (SiO₂), likely chert/flint
sedimentary
Yellow chert or jasper pebble
Microcrystalline quartz (SiO₂), likely iron-oxide-stained chert/jasper
sedimentary
White coral limestone (probable fossiliferous limestone)
Calcite (CaCO₃), commonly derived from aragonitic coral skeletons recrystallized to calcite
sedimentary
Mother of Pearl (Nacre)
Calcium Carbonate (Aragonite) with organic conchiolin
gemstone
Rounded reddish-brown pebble, likely iron-stained quartzite or chert
Quartzite (mostly SiO₂), possibly ferruginous chert
metamorphic
Rounded flint or chert pebble
Microcrystalline quartz (SiO₂), commonly chalcedony with possible impurities
sedimentary
Cleavable Calcite
Calcium Carbonate (CaCO3)
mineral
Tumbled chert or chalcedony pebble
Microcrystalline quartz (SiO₂), likely chert/chalcedony
sedimentary
Flint or chert fragment
Microcrystalline quartz (SiO₂), commonly chalcedony with possible iron-oxide impurities
sedimentary
Pearl (as a Biogenic Mineral)
Calcium Carbonate (mostly Aragonite) with Conchiolin; CaCO3
mineral
Pearl
Calcium carbonate (CaCO3) in the form of Aragonite or Calcite
mineral
Stromatolite
Biogenic sedimentary rock / Stromatolite
sedimentary
Carbonate Beach Sand
Biogenic Carbonate Sediment (CaCO3)
sedimentary
Stromatolite
Biogenic sedimentary rock / Stromatolite
sedimentary
Fossiliferous Limestone
Biogenic Sedimentary Rock (CaCO3)
sedimentary
Pearl
Biogenic CaCO3 (Aragonite and Calcite)
mineral
Fossiliferous Limestone
Biogenic Calcium Carbonate (CaCO3)
sedimentary
Brachiopod Fossil
Phylum Brachiopoda (likely Order Rhynchonellida or Spiriferida)
sedimentary
Banded chert or jasper pebble
Microcrystalline quartz (SiO₂), likely chert/jasper with iron-oxide staining
sedimentary
Chert (likely flint-bearing chert)
Microcrystalline quartz, SiO₂ (chalcedony/quartz aggregate)
sedimentary
Chert or silicified rock fragment
Microcrystalline quartz (SiO₂), likely chert with iron-oxide staining
sedimentary
Pearl
Calcium Carbonate (Aragonite and Calcite), CaCO3
mineral
Precious Red Coral
Corallium rubrum (Calcium Carbonate, CaCO3)
mineral