Dark river pebble (likely basalt or andesite)
Fine-grained mafic/intermediate volcanic rock; commonly basalt (plagioclase ± pyroxene/olivine)
igneous
Category
Mineral, Possibly Rock Fragment Containing A Mineral
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Weathered limestone or calcareous fossil fragment
Calcite-rich carbonate rock (CaCO₃), possibly fossiliferous limestone
sedimentary
Sandstone (likely Arkosic)
Clastic Sedimentary Rock (Sandstone)
sedimentary
Granite
Intrusive Igneous Rock
igneous
Sandstone (likely Arkosic or Lithic Sandstone)
Arenite (composed primarily of SiO2 with various lithic fragments)
sedimentary
Weathered granite or granodiorite fragment
Granite–granodiorite, chiefly quartz, feldspar, and dark biotite/amphibole
igneous
Sandstone Beach Pebble
Clastic Sandstone (SiO2 - Quartz-dominant)
sedimentary
Sandstone
Sandstone (clastic sedimentary rock)
sedimentary
Conglomerate
Conglomerate (Clastic sedimentary rock)
sedimentary
Sandstone
Arenite (SiO2 primarily)
sedimentary
Turquoise
CuAl6(PO4)4(OH)8·4H2O
mineral
Sandstone (Micaceous)
Arenite (composed primarily of SiO2)
sedimentary
Quartz Geode Fragment
Silicon Dioxide (SiO2)
mineral
Felsic Tuff
Pyroclastic volcanic rock (Tuff)
igneous
Tumbled serpentine with dark magnetite/chromite matrix
Serpentinite; chiefly antigorite/lizardite, Mg3Si2O5(OH)4, with magnetite and possibly chromite
metamorphic
Likely tumbled yellow calcite or limestone fragment
Calcite (CaCO₃), possibly micritic limestone
mineral
Sandstone (Quartzose)
Arenite (primarily SiO2)
sedimentary
Fossil Shell Fragment (possibly Brachiopod or Bivalve)
Calcium Carbonate (CaCO3) - Phylum Brachiopoda or Mollusca
sedimentary
Fossilized Bone
Petrified Bone (Fluorapatite / Calcium Phosphate replacement)
fossil
Conglomerate
Conglomerate (clastic sedimentary rock)
sedimentary
Granite Pebble
Intrusive Igneous Rock
igneous
Sandstone
Quartz Sandstone (predominantly)
Sedimentary
Conglomeratic sandstone or breccia
Lithic arkose / polymictic conglomeratic sandstone
sedimentary
Granite
Felsic intrusive igneous rock
igneous
Unidentified gray stone
Likely quartz-rich stone; exact identification is not possible from the image
mineral
Metallic sulfide ore, likely pyrite-bearing rock
Pyrite (FeS₂), possibly with chalcopyrite and quartz/host rock
mineral
Granitic Pegmatite (River Rock specimen)
Granite / Pegmatite (composed of SiO2, KAlSi3O8, and NaAlSi3O8)
igneous
Amygdaloidal Basalt
Amygdaloidal Basalt (Mafic volcanic rock)
igneous
Sandstone (Quartz-rich)
Clastic sedimentary rock (SiO2 primary)
sedimentary
Graywacke
Graywacke Sandstone
sedimentary
Tumbled Amethyst
Quartz (Silicon Dioxide, SiO2, colored by iron impurities)
mineral
Sandstone (River Cobble)
Clastic Sedimentary Rock (primarily Quartz with Feldspar)
sedimentary
Kimberlite with Diamonds
Kimberlite (ultramafic potassic igneous rock)
igneous
Likely galena-bearing ore
Galena (lead sulfide, PbS), possibly mixed with quartz or other sulfides
mineral
Sandstone (Quartz-rich)
Arenite (SiO2 based clastic rock)
sedimentary
Sandstone (with Chert/Quartzite)
Arenite (primarily SiO2)
sedimentary
Quartz / Common Opal Transition
Silicon Dioxide (SiO2)
mineral
Red Sandstone
Arenite (Ferruginous Sandstone)
sedimentary
Sandstone
Clastic sedimentary rock (primarily SiO2)
sedimentary
Conglomerate
Conglomerate (SiO2 matrix with varying clasts)
sedimentary
Basalt
Mafic Igneous Rock (primarily Plagioclase Feldspar and Pyroxene)
igneous
Quartz Geode Fragment
Silicon Dioxide (SiO2)
mineral