Rock (Likely Sedimentary)

Asphalt aggregate

Human-made bituminous asphalt containing crushed silicate rock aggregate

Conglomerate

Conglomerate (clastic sedimentary rock)

Sandstone

Clastic Sedimentary Rock (composed mostly of quartz, SiO2)

Chalcedony (Common Agate)

Silicon Dioxide (SiO2)

Rounded sandstone pebble

Quartz-rich sandstone, likely ferruginous or clay-rich

Pebble / Gravel

Clastic Sedimentary Specimen (likely Limestone or Quartzite base)

Sandstone (Pebble)

Arenite (primarily SiO2)

Iron-rich breccia (likely limonite/goethite-stained rock)

Ferruginous breccia; iron oxides/hydroxides such as goethite (FeO(OH)) and limonite, with unidentified rock fragments

Small rounded pebble

Indeterminate lithic clast; likely weathered quartzite, sandstone, or chert

Sandstone

Arenite (specifically Iron-stained Quartz Sandstone)

Tumbled tan stone, possibly sandstone or weathered limestone

Indeterminate; likely quartz-rich sandstone or calcitic limestone

Chert / Chalcedony (likely carnelian or flint variety)

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2) within Sedimentary or Igneous host

Rounded quartz-rich pebble

Chert or quartzite pebble (tentative; mostly microcrystalline quartz, SiO₂)

Fossiliferous Limestone

Biogenic Limestone (Calcium Carbonate, CaCO3)

Jasper

Chalcedony (Microcrystalline Quartz) - SiO2

Quartz Geode

Silicon Dioxide (SiO2) in Calcareous or Siliceous Matrix

Possible iron-rich nodule or weathered ironstone

Limonite/goethite-rich concretion; commonly represented as FeO(OH)·nH₂O with iron oxides

Rounded yellow river pebble

Likely quartz-rich sandstone or weathered chert; exact identification requires a hardness and acid test

Sandstone (with Iron Staining)

Clastic sedimentary rock (primarily SiO2)

Weathered sandstone or iron-stained sedimentary rock

Quartz-rich clastic sandstone; exact identification requires testing

Banded Gneiss

Gneiss (complex metamorphic silicate rock)

Weathered iron-stained stone, likely graywacke or altered sandstone

Indeterminate lithic fragment; probable quartz-rich sandstone/graywacke with iron-oxide staining

Sandstone (likely Arkose or Quartz Sandstone)

Clastic sedimentary rock (primarily SiO2)

River Cobble with Algae Patina

Weathered Chert or Quartzite pebble (SiO2 dominated)

Weathered gray sandstone or siltstone

Clastic sedimentary rock, likely quartz–feldspar sandstone/siltstone

Sandstone (likely Arkose or Lithic)

Clastic sedimentary rock (SiO2 + impurities)

Rounded river cobble, likely weathered sandstone or siltstone

Quartz-rich clastic sedimentary rock; exact identification requires a fresh surface and testing

Weathered quartz-rich pebble, possibly quartzite or chert

Quartz (SiO₂), possibly quartzite; exact identification is uncertain from the image

Dyed Agate Slice

Silicon Dioxide (SiO2)

Sandstone (likely Quartzose)

Arenite (primarily SiO2)

Vuggy Limestone

Carbonate Sedimentary Rock with Vuggy Porosity (CaCO3)

Sandstone (Quartz-rich)

Arenite (Quartz Arenite)

Sandstone (Graywacke type)

Clastic Sedimentary Rock (Lithic Sandstone)

Fossiliferous Limestone

Calcium Carbonate (CaCO3)

Rounded gray stone, likely weathered chert or quartz-rich river pebble

Chert (microcrystalline SiO₂), tentative

Polished opal-bearing rock (likely boulder opal)

Opal, hydrated amorphous silica (SiO₂·nH₂O), in ironstone or host rock

Sandstone (Banded)

Arenite (SiO2 with iron oxide impurities)

Rounded brown river pebble

Indeterminate; likely weathered sandstone or iron-stained quartzite

Sandstone (likely Arkose or Quartz Sandstone)

Clastic sedimentary rock (primarily SiO2)

Smoky Quartz and Biotite Schist

Quartz-Biotite Schist (SiO2 + K(Mg,Fe)3AlSi3O10(F,OH)2)

Quartz-rich pegmatitic rock, probably granitic gneiss

Quartz–feldspar–mica gneiss; locally pegmatitic granite