Rock (Likely Sedimentary)

Sandstone (Quartzose Sandstone)

Clastic Sedimentary Rock (Lithic arenite / Quartz arenite)

Weathered iron-rich sandstone or ferruginous quartzite

Ferruginous sandstone; chiefly quartz (SiO₂) with iron oxides/hydroxides

Likely weathered quartz-rich rock fragment

Indeterminate; possibly quartz-bearing sandstone or chert with iron-oxide staining

Weathered iron-rich rock, possibly basalt or limonite-bearing sandstone

Undetermined; likely Fe-oxide-stained basalt or ferruginous sandstone (hematite/goethite-bearing)

Tumbled brown jasper / iron-rich breccia

Microcrystalline quartz (SiO₂), likely with iron oxides and assorted silicate fragments

Sandstone

Arenite (SiO2-rich)

Riverstone (likely Gray Slate or Siltstone)

Metamorphosed fine-grained sedimentary rock (Argillite/Slate)

Likely weathered quartz-bearing rock fragment

Provisional identification: quartz-rich sandstone or microcrystalline quartz (SiO₂)

Rounded gray-brown cobble, likely weathered sandstone or quartz-rich sedimentary rock

Probable lithic sandstone; exact identification requires a fresh surface and hardness/streak tests

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Sandstone Pebble (Ventifact)

Arenite (mostly SiO2)

Yellow Chert (Cherty Pebble)

Silicon Dioxide (SiO2)

Chert (Jasper/Flint variety)

Silicon Dioxide (SiO2)

Weathered sandstone or limestone fragment

Likely quartz-rich sandstone or calcitic limestone; exact identification is uncertain from the image

Gneiss (Green Gneiss)

Gneiss (High-grade Regional Metamorphic Rock)

Weathered sandstone or iron-rich sedimentary rock

Quartz-rich arenite, possibly ferruginous sandstone

Chert Conglomerate (or Breccia)

Sedimentary Clastic Rock (variety: Ferruginous Chert Breccia)

Sandstone

Arenite (composed primarily of SiO2)

Sandstone (likely Quartz Sandstone)

Arenite (composed primarily of SiO2)

Likely shale or mudstone fragment

Fine-grained clastic sedimentary rock, composed mainly of clay minerals and silt-sized quartz; the image is insufficient to distinguish shale from mudstone confidently.

Sandstone (clastic)

Clastic Sedimentary Rock (primarily composed of SiO2)

Sandstone

Arenite (primarily SiO2)

Rounded yellow-brown river pebble

Indeterminate lithology; possibly weathered sandstone or chert

Mixed river stones and gravel

Polymictic alluvial clasts; individual pieces may include quartzite, granite, basalt, sandstone, limestone, and slate

Sandstone (Green/Yellow Siltstone variant)

Arenite or Siltstone (primarily SiO2 with mineral staining)

Quartz Geode

Quartz (Silicon Dioxide - SiO2) within a Chalcedony and Limonite shell

Rounded quartz-rich pebble, possibly chert or weathered sandstone

Indeterminate siliciclastic rock; likely microcrystalline quartz (SiO₂) or quartz-feldspar sandstone

Weathered gray metamorphic rock, likely gneiss or schist

Probable quartz–feldspar–mica gneiss/schist; exact identification requires a fresh surface and tests

Unidentified pale sedimentary rock, likely limestone

Calcite-rich limestone (CaCO₃), possibly fossiliferous or weathered micritic limestone

Sandstone

Arenite (primarily SiO2)

Sandstone (Greywacke/Lithic Sandstone)

Arenite (composed primarily of SiO2)

Banded Chert or Agate

Silicon Dioxide (SiO2)

Sandstone (Weathered)

Arenite (primarily SiO2)

Sandstone (likely Fossilized Wood or Concrete Simulacrum)

Arenite / Silicified Wood / Anthropogenic Concrete

Unidentified Rock Fragment

Unknown

Rounded river pebble, likely quartz-rich chert or fine-grained sandstone

Indeterminate lithic clast; possible microcrystalline quartz (chert) or quartz-rich sandstone

Likely weathered sandstone or iron-stained quartz fragment

Quartz-rich sandstone; predominantly SiO₂ with iron-oxide staining

Rounded gray pebble

Indeterminate; likely fine-grained quartz-rich silicate rock

Weathered graywacke or sandstone fragment

Lithic sandstone, likely quartz–feldspar–rock-fragment aggregate

Weathered granitic rock

Granite or granodiorite; mainly quartz, feldspar, and mica/amphibole

Quartz-bearing metamorphic rock, possibly quartzite or hornfels

Mostly quartz (SiO₂), with probable iron-oxide and dark silicate minerals

Rounded quartz-rich river pebble

Lithic clast, likely quartzite or fine-grained sandstone