Agate
Agate (Cryptocrystalline variety of Quartz, SiO2)
mineral
Category
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Grey Agate
Silicon Dioxide (SiO2) - Variety of Chalcedony
mineral
Chert / Flint
Microcrystalline Quartz (SiO2)
sedimentary
Quartz Vein in Mica Schist
Quartz (SiO2) with Muscovite/Biotite Schist
metamorphic
Chert (often called Jasper or River Siltstone)
Chert (SiO2)
sedimentary
Ferruginous Quartz
Quartz with Iron Oxide inclusions (SiO2 + Fe2O3)
mineral
Glacial Erratic (Sandstone/Quartzite)
Glacial Erratic specimen (likely Orthoquartzite or Feldspathic Sandstone)
sedimentary or metamorphic
Sandstone Concretion
Ferruginous Sandstone Concretion (Primarily SiO2 with Iron Oxide cement)
sedimentary
Chert (Flint)
Chert (Microcrystalline Quartz, SiO2)
sedimentary
Quartz (Smoky/Druzy variety)
Silicon Dioxide (SiO2)
mineral
Quartz Geode Fragment
Silicon Dioxide (SiO2)
mineral
Crinoid Fossil Marble
Crinoidal Limestone / Phylum Echinodermata
sedimentary
Quartz (Milky/Common)
Quartz (Silicon Dioxide, SiO2)
mineral
Garnet-Bearing Schist
Almandine Garnet Micaceous Schist
metamorphic
Amygdaloidal Basalt
Amygdaloidal Basalt
igneous
Biotite Schist
Biotite Mica Schist (K(Mg,Fe)3AlSi3O10(OH,F)2)
metamorphic
Sandstone Concretion
Ferruginous Sandstone Concretion (SiO2 + FeO(OH))
sedimentary
Grey Agate (Tumbled)
Silicon Dioxide (SiO2)
mineral
Chert (often called Flint in dark varieties)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Amethyst (Scepter/Double Terminated Point)
Silicon Dioxide (SiO2)
mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Chert (Iron-stained)
Chert (Cryptocrystalline Silica, SiO2)
sedimentary
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Chert (Jasper variety)
Silicon Dioxide (SiO2)
sedimentary
Conglomerate
Conglomerate (Clastic sedimentary rock)
sedimentary
Quartz with Hematite
Silicon Dioxide (SiO2) with Ferric Oxide (Fe2O3)
mineral
Desert Rose (Baryte or Gypsum Rose)
Baryte (BaSO4) or Gypsum (CaSO4·2H2O)
mineral
Granite Pebble
Granite (composed mainly of Quartz, Feldspar, and Mica)
igneous
Concrete Fragment
Hardened Portland cement and mineral aggregate
sedimentary (anthropogenic)
Sandstone with Liesegang Rings
Arenite with Iron Oxide Concretions
sedimentary
Porphyritic Basalt
Basalt (with plagioclase phenocrysts)
igneous
Quartzite River Rock
Quartzite (SiO2)
metamorphic
River Rock (Mossy)
Stream-rounded Clast (likely Siltstone or Sandstone with bryophytes)
sedimentary
Conglomerate
Conglomerate (Clastic Sedimentary Rock)
sedimentary
Quartz Geode (partially formed/chalcedony with iron staining)
Quartz (SiO2) with Chalcedony (cryptocrystalline quartz) and likely Iron Oxides/Hydroxides
Mineral/Sedimentary Rock Feature
Shale or Mudstone (Based on appearance)
Shale (fine-grained, laminated fissile sedimentary rock) / Mudstone (fine-grained, non-fissile sedimentary rock)
Sedimentary
Blue Chalcedony
Silicon Dioxide (SiO2)
mineral
Conglomerate
Clastic sedimentary rock (Conglomerate)
sedimentary
Quartz (Pebble)
Quartz (SiO₂)
Mineral
Sandstone
Arenite (composed primarily of SiO2)
sedimentary
Folded Schist / Gneiss (Metamorphic Rock)
Regional Metaphoric Folded Outcrop (predominantly Schist/Gneiss)
metamorphic
Sandstone
Clastic sedimentary rock (primarily SiO2)
sedimentary