Garnet Schist
Almandine Garnet Schist (Fe3Al2(SiO4)3 in Schistose matrix)
metamorphic
Category
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Marble
Recrystallized Calcite (CaCO3)
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
Tumbled yellow chalcedony (likely yellow jasper)
Microcrystalline quartz, SiO₂; chalcedony/jasper variety
mineral
Sandstone (Lithic Arenite)
Clastic Sedimentary Rock (primarily SiO2)
sedimentary
Sandstone
Clastic sedimentary rock
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
Chalk
Calcium Carbonate (CaCO3)
sedimentary
Banded Agate (with Quartz Geode Center)
Silicon Dioxide (SiO2)
mineral
Orgonite Pyramid (containing Amethyst and mixed minerals)
Silicon Dioxide (SiO2) in synthetic resin
gemstone
Mica
Phlogopite or Biotite group (KMg3(AlSi3O10)(F,OH)2 / K(Mg,Fe)3AlSi3O10(OH)2)
mineral
Orthoceras fossil in limestone
Orthoceras (extinct genus of cephalopod)
sedimentary
Tumbled banded agate
Microcrystalline quartz (chalcedony), SiO₂, with band-forming impurities
mineral
Banded iron formation fragment (polished ironstone)
Banded iron formation; hematite/magnetite-rich chert, commonly approximated as Fe₂O₃–Fe₃O₄ with SiO₂
sedimentary
Barite
Barium sulfate (BaSO4)
mineral
Orthoceras Fossil
Orthoceras regulare (Class Cephalopoda, Order Orthocerida)
fossil
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
Tumbled jasper, likely picture or brecciated jasper
Microcrystalline quartz (SiO₂) with iron-oxide and other mineral impurities
gemstone
Orange Moss Agate / Carnelian Agate
Silicon dioxide (SiO2) - variety Chalcedony
sedimentary
Sandstone (Water-worn Cobble)
Arenite (variable composition, primarily SiO2)
sedimentary
Kaolin Clay in Saprolite Profile
Kaolinite (Al2Si2O5(OH)4) within Weathered Pegmatite/Granite
sedimentary
Orthoceras Fossil in Limestone
Orthoceras regulare
sedimentary
Banded Iron Formation (BIF)
Banded Iron Formation (BIF)
sedimentary
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
Rounded gray river pebble, likely granite or gneiss
Indeterminate granitic rock; commonly quartz + feldspar + mica, possibly gneissic
igneous
Rounded quartz-rich pebble, likely sandstone or granitic-derived pebble
Indeterminate clastic rock; likely quartz-rich sandstone/conglomerate clast
sedimentary
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Sandstone
Clastic sedimentary rock (primarily SiO2)
sedimentary
Muscovite Mica
Muscovite (KAl2(AlSi3O10)(OH)2)
mineral
Sandstone (Calcareous or Quartz-rich)
Arenite
sedimentary
Sandstone
Arenite (SiO2 principal)
sedimentary
Sandstone (Ferruginous)
Arenite (composed primarily of SiO2 with Fe2O3 cement)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary