Petrified Wood
Silicified wood (Quartz/Chalcedony replacement of cellulose)
fossil
Category
Organic (Paper And Cellulose)
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Quartzite River Rock
Quartzite (primarily SiO2)
metamorphic
Pyrite
Iron Disulfide (FeS2)
mineral
Fossil Coral (Petoskey Stone / Hexagonaria)
Hexagonaria percarinata (Silicified/Calcite Replacement Coral)
fossil
Kaolinite (China Clay)
Kaolinite (Al2Si2O5(OH)4)
sedimentary
Petoskey Stone (Fossilized Rugose Coral)
Hexagonaria percarinata
fossil
Chalk
Micrite (primarily Calcium Carbonate or CaCO3)
sedimentary
Grey Banded Agate
Chalcedony (Silicon Dioxide, SiO2)
mineral
Marble
Recrystallized Calcite (CaCO3)
metamorphic
Garnet Schist
Almandine Garnet Schist (Fe3Al2(SiO4)3 in Schistose matrix)
metamorphic
Petoskey Stone
Hexagonaria percarinata
sedimentary
Agate (Geode nodule)
Cryptocrystalline Quartz (SiO2)
mineral
Tumbled greenstone/chlorite-rich pebble
Likely chlorite-rich greenschist or altered basalt; exact identification requires testing
metamorphic
Sandstone (Pebble)
Sandstone (SiO2 with matrix/cement)
sedimentary
Agate Bookend / Quartz Geode
Silicon Dioxide (SiO2)
mineral
Petoskey Stone
Hexagonaria percarinata
fossil
Pet Rock (Man-made Quartzite or Granite Cobble)
Silicon dioxide (SiO2) mixture; commonly composed of Quartz, Feldspar, and Mica
igneous or metamorphic (base stone); anthropogenic (decoration)
Petoskey Stone
Hexagonaria percarinata
sedimentary
Petoskey Stone
Hexagonaria percarinata (Fossilized Rugose Coral)
sedimentary
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Sandstone
Clastic sedimentary rock
sedimentary
Sandstone (Lithic Arenite)
Clastic Sedimentary Rock (primarily SiO2)
sedimentary
Graphite
Graphite (C)
mineral
Ferruginous Sandstone
Arenite with limonite/goethite cement
sedimentary
Gypsum Wallboard (Drywall)
Hydrous calcium sulfate (CaSO4·2H2O)
sedimentary (processed mineral product)
Ferruginous Sandstone
Arenite with Iron-Oxide Cement
sedimentary
Mica
Phlogopite or Biotite group (KMg3(AlSi3O10)(F,OH)2 / K(Mg,Fe)3AlSi3O10(OH)2)
mineral
Sandstone (Iron-stained)
Sandstone (dominated by Quartz, SiO2, with Iron Oxide impurities)
sedimentary
Sandstone
Arenite (SiO2 primarily)
sedimentary
Sandstone (Lithic Sandstone / Greywacke)
Sandstone (SiO2 rich clastic sedimentary rock)
sedimentary
Chalk
Calcium Carbonate (CaCO3)
sedimentary
Banded Agate (with Quartz Geode Center)
Silicon Dioxide (SiO2)
mineral
Orthoceras fossil in limestone
Orthoceras (extinct genus of cephalopod)
sedimentary
Orgonite Pyramid (containing Amethyst and mixed minerals)
Silicon Dioxide (SiO2) in synthetic resin
gemstone
Tumbled jasper, likely picture or brecciated jasper
Microcrystalline quartz (SiO₂) with iron-oxide and other mineral impurities
gemstone
Ammonite Fossil in Matrix
Ammonoidea subclass (e.g., Arietites or similar genera)
fossil
Banded Agate (Dyed / Polished)
Microcrystalline Quartz (SiO2)
mineral
Dyed Agate Geode
Silicon Dioxide (SiO2) - Banded Chalcedony
mineral
Barite
Barium sulfate (BaSO4)
mineral
Orthoceras Fossil
Orthoceras regulare (Class Cephalopoda, Order Orthocerida)
fossil
Orange Moss Agate / Carnelian Agate
Silicon dioxide (SiO2) - variety Chalcedony
sedimentary
Sandstone (Water-worn Cobble)
Arenite (variable composition, primarily SiO2)
sedimentary