Rock (Likely Sedimentary)

Chalcedony Nodule (Commonly known as Agate or Chert)

Microcrystalline Quartz (SiO2)

Likely weathered quartz-rich rock, possibly smoky quartz or chert

Quartz (SiO₂), though exact identification is uncertain from the photograph

Fossilized Gastropod in Limestone

Gastropoda (Class) in Fossiliferous Limestone

Weathered iron-rich concretion or laterite fragment

Ferruginous concretion, likely goethite/limonite (hydrated iron oxides) in a clay-rich matrix

Tumbled serpentine with dark magnetite/chromite matrix

Serpentinite; chiefly antigorite/lizardite, Mg3Si2O5(OH)4, with magnetite and possibly chromite

Banded Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Pyritic Sandstone

Clastic Sedimentary Rock (Pyrite-bearing Sandstone)

Fossiliferous Limestone with Rugose Coral

Calcite (CaCO3) matrix containing Rugosa (order of extinct solitary and colonial corals)

Basalt Porphyry

Porphyritic Basalt

Chert (Polished/Tumbled)

Silicon Dioxide (SiO2)

Chert (Yellow or Ochre Jasper variant)

Microcrystalline Quartz (SiO2)

Jasper with Quartz Druzy

Silicon Dioxide (SiO2)

Sandstone River Cobble

Arenite (predominantly SiO2)

Hardened Gray Mudstone

Argillite / Silicified Mudstone (principally SiO2 and Al2Si2O5(OH)4)

Banded Gneiss

Gneiss (Metamorphic Rock)

Sandstone (Ferruginous)

Arenite (with Iron Oxide cement)

Weathered sandstone

Quartz-rich clastic sandstone, likely iron-oxide-stained

Sandstone (Ferruginous)

Clastic sedimentary rock (primarily SiO2 with Fe2O3 cement)

Marble

Recrystallized Calcite Rock (CaCO3)

River Pebble (Gneiss or Quartzite variant)

Metamorphic rock specimen (likely Quartzite or Gneiss)

Sandstone (likely Quartzose Sandstone)

Arenite (primarily SiO2)

Chert (specifically a weathered Chert nodule or fragment)

Chert; Microcrystalline or Cryptocrystalline Quartz (SiO2)

Quartz-rich rock, likely chert or chalcedony

Microcrystalline silica (SiO₂), possibly quartz/chalcedony

Granite-like igneous rock

Likely medium-grained granite or granodiorite; quartz–feldspar–mica aggregate

Granite or Pegmatite in host rock

Granitoid / Felsic Intrusive Rock

Mixed collection of natural stones

Several unidentified lithologies, likely including basalt, granite, quartzite, sandstone, and weathered metamorphic rocks

Druzy Quartz on Matrix (likely Limestone or Sandstone)

Silicon Dioxide (SiO2) with various trace impurities

Rounded reddish-brown pebble

Likely ferruginous sandstone or iron-rich quartzite; exact identification requires a fresh surface and tests

Sandstone (likely Greywacke variant)

Arenite

Feldspar-rich Quartzite

Meta-arkose (Quartz-Feldspar Quartzite)

Sandstone (likely Arkosic or Lithic Sandstone)

Sandstone (SiO2 predominant)

Sandstone (likely Graywacke or Arkose variant)

Clastic Sedimentary Rock (SiO2 dominated)

Iron-stained quartz (likely quartzite or quartz-rich rock)

Quartz, silicon dioxide (SiO₂), with iron-oxide staining

Weathered sandstone or iron-rich sedimentary cobble

Quartz arenite to ferruginous sandstone; predominantly SiO₂ (quartz) with iron-oxide cement

Sandstone (likely Arkosic or Lithic Sandstone)

Clastic Sedimentary Rock (SiO2 with assorted minerals)

River Cobble (Mixed Lithology)

Clastic Sedimentary Rock (Silicified Siltstone or Wacke)

Ironstone (likely Ferruginous Siltstone/Sandstone)

Ferruginous sedimentary rock (FeOx-rich clastic)

Quartz Druze on Matrix

Silicon Dioxide (SiO2)

Garnet-Bearing Gneiss

Garnetiferous Feldspathic Gneiss

Fossiliferous Chert

Cryptocrystalline quartz (SiO2) with biogenic inclusions

Weathered limestone or calcitic fossil/reef fragment

Calcite-rich limestone (CaCO₃), possibly fossiliferous limestone

Hard Sandstone (Quartzite)

Quartz-rich Sedimentary Rock (Proto-Quartzite)