Chert (specifically Flint or Dark Chert)
Chert (SiO2)
sedimentary
Category
Sedimentary (Fossilized Organic Remain)
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Sandstone (with Iron Staining)
Clastic Sedimentary Rock (primarily Quartz, SiO2)
sedimentary
Fossiliferous rock fragment (possible shell fossil)
Likely a calcium-carbonate fossil in limestone; exact fossil and host rock are not identifiable from the image
fossil
Coal (Bituminous)
Sedimentary carbonaceous rock
sedimentary
Rounded quartz-rich cobble, possibly quartzite or granitic rock
Indeterminate; likely quartz–feldspar aggregate, potentially weathered granite or quartzite
igneous
Ammonite Fossil
Ammonoidea (primarily composed of Calcite, CaCO3)
sedimentary
Polished amber
Amber (fossilized plant resin), commonly succinite; organic mineraloid rather than a true mineral
gemstone
Chalcedony (Agate/Seashell replacement)
Silicon Dioxide (SiO2) - Cryptocrystalline Quartz
mineral
Amber
Fossilized tree resin; primarily polymerized terpenoid resin (succinite)
gemstone
Kambaba Jasper
Stromatolite / Fossilized Algae (Rhyolitic structure)
sedimentary
Ironstone Concretion / Chert Nodules
Iron-rich Sedimentary Concretion (Fe2O3 / SiO2 mix)
sedimentary
Banded Gneiss
Gneiss (High-grade Regional Metamorphic Rock)
metamorphic
Quartzite with Mafic Inclusions
Metamorphic Quartzite
metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Quartzite
Metamorphosed Quartz Sandstone
metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Coal
Coal (Combustible sedimentary rock)
sedimentary
Sandstone
Arenite
sedimentary
Tiger's Eye (Rough)
Pseudomorph of Quartz after Crocidolite (SiO2 with FeOOH inclusions)
metamorphic
Sandstone Concretion
Clastic sedimentary rock (primarily Silica, SiO2, or Calcium Carbonate, CaCO3)
sedimentary
Sandstone
Arenite (SiO2 primarily)
sedimentary
Sandstone (Ferruginous)
Arenite (primarily SiO2 with Fe2O3 staining)
sedimentary
Limpets Shell / Fossil Specimen
Patellogastropoda (Class)
fossil
Greywacke with Quartz Vein
Matrix: Impure Sandstone (SiO2 + varied clasts), Veins: Quartz (SiO2)
sedimentary
Flint / Chert (Fossiliferous)
Silicon dioxide (SiO2) with microcrystalline quartz
sedimentary
Kambaba Jasper
Rhyolite (with Stromatolite fossil inclusions)
sedimentary
Fossilized Rugose Coral (Petoskey Stone type)
Hexagonaria percarinata (Order: Rugosa)
sedimentary
Probable fossilized coral
Fossil coral; exact coral group and species cannot be determined from the image
fossil
Amber
Succinite (specifically for Baltic amber); C10H16O (Variable organic compound)
mineral
Fossil Coral
Cnidaria fossil (often Calcium Carbonate / CaCO3)
sedimentary
Amber
Succinite (Formula: C10H16O)
Organic Mineraloid
Sandstone Pebble
Arenite (SiO2 complex)
sedimentary
Sandstone
Arenite (SiO2 principal)
sedimentary
Sandstone
Arenite (SiO2 variety)
sedimentary
Backlit translucent mineral specimen, possibly amber or orange calcite
Undetermined; visual appearance alone cannot distinguish amber from calcite or other translucent minerals
mineral
Fossilized Brachiopod Shell Fragment
Brachiopoda (Class: Rhynchonellata or Strophomenata)
fossil
Amber
Fossilized plant resin; chiefly an organic polymer (succinite), not a crystalline mineral
gemstone
Fossilized Oyster Shell
Ostreidae (Calcium Carbonate - CaCO3)
fossil
Fossilized oyster or bivalve shell
Fossil Gryphaeidae or Ostreoidea; calcitic shell, CaCO₃
fossil
Crinoid Stem Fossil (Indian Bead)
Crinoid ossicle (Echinodermata)
fossil
Unakite
Epidotized Granite
metamorphic
Unakite
Altered granitic rock (epidosite/unakite)
metamorphic