Travertine (Tufa)
Chemical Sedimentary Rock / Travertine (CaCO3)
sedimentary
Category
Organic Structure (Not A Rock)
Browse organic structure (not a rock) specimens identified by the Rock Identifier community.
Learn about Organic Structure (Not A Rock) in the encyclopedia
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Fossiliferous Limestone
Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)
sedimentary
Fossiliferous Limestone
Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)
sedimentary
Chert (Jasper/Flint variant)
Microcrystalline quartz (SiO2)
sedimentary
Sandstone Chert Concretion
Silica-cemented Concretion (primarily SiO2)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Chert (Septarian or Nodular variety)
Microcrystalline Quartz (SiO2)
sedimentary
Concretionary Sandstone
Clastic Sedimentary Rock (Sandstone with secondary mineral cementation)
sedimentary
Chert (River Pebble)
Microcrystalline Quartz (SiO2)
sedimentary
Chert (Jasper/Flint variety)
Silicon Dioxide (SiO2)
sedimentary
Chert (Nodular Chert)
Silicon Dioxide (SiO2)
sedimentary
Chert (Common Opal/Jasper variety)
Microcrystalline Quartz (SiO2) with hydration
sedimentary
Fossil bivalve shell
Likely an extinct or modern-like ribbed cockle/scallop; exact genus requires locality and diagnostic hinge features
fossil
Chert (River Pebble)
Silicon Dioxide (SiO2)
sedimentary
Precious Red Coral
Corallium rubrum (Calcium Carbonate, CaCO3)
gemstone
Petrified Wood
Silicified Wood (SiO2)
metamorphic
Banded Chert (River Siltstone)
Microcrystalline Quartz (SiO2)
sedimentary
Chert (Flint/Jasper variety)
Microcrystalline Quartz (SiO2)
sedimentary
Weathered limestone or calcareous fossil fragment
Calcite-rich carbonate rock (CaCO₃), possibly fossiliferous limestone
sedimentary
Amber (Rough Baltics/Beach Specimen)
Succinicum (Organic Gemstone - Fossilized Resin)
mineral
Chert (Flint Pebbles)
Chert (SiO2)
sedimentary
Fossiliferous Sandstone / Fossil Fragment
Fossiliferous Sedimentary Matrix with Indeterminate Fossil Material
fossil
Glauconite (Green Sandstone)
Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2
sedimentary
Petrified Wood
Silicified Wood (SiO2)
Mineral / Fossil
Red Coral
Corallium rubrum
gemstone
Petrified Wood
Silicified wood (primarily Silicon Dioxide, SiO2)
metamorphic
Petrified Wood
Silicified wood (primarily Quartz, SiO2)
fossil
Polished plume agate
Chalcedony (microcrystalline SiO₂) with iron-oxide inclusions
mineral
Shale with Vein Infillings
Shale (a fine-grained clastic sedimentary rock). The veins could be Calcite (CaCO3), Quartz (SiO2), or other minerals.
Sedimentary Rock
Chert / Jasper
Cryptocrystalline Silica (SiO2)
sedimentary
Ammonite Fossil (Small Pyritized or Calcitized Internal Mold)
Ammonoidea
sedimentary
Chert (Chert / Flint)
Silicon dioxide (SiO2) - Microcrystalline quartz
sedimentary
Tumbled black stone, likely black agate or onyx
Microcrystalline quartz (SiO₂), probably chalcedony/black agate; exact identification requires testing
mineral
Chert (Field Stone)
Microcrystalline / Cryptocrystalline Quartz (SiO2)
sedimentary
Fossiliferous Limestone (Crinoid stem)
CaCO3 (Calcium Carbonate) with Fossil Inclusions
sedimentary
Chert Pebble
Microcrystalline or cryptocrystalline Quartz (SiO2)
sedimentary
Tumbled brown chalcedony or quartzite pebble
Microcrystalline quartz (SiO₂), likely chalcedony; exact identification requires testing
mineral
Chert (Arrowhead/Artifact Fragment)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Petrified Wood
Silicified wood (Quartz/Chalcedony replacement of organic matter)
fossil
Chert (Quartz Variety)
Chert (mostly SiO2 / Silicon Dioxide)
sedimentary
Likely pyrite-bearing rock fragment
Pyrite, FeS₂, possibly in a dark host rock
mineral
Red Jasper
Jasper (Silicon Dioxide, SiO2)
sedimentary