Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Geode (Chert/Quartz Nodule)

Silicon Dioxide (SiO2)

Basalt

Basalt (Mafic volcanic rock)

Likely fossiliferous limestone fragment

Calcareous fossil assemblage, chiefly calcium carbonate (CaCO₃), possibly crinoid, bivalve, or bryozoan material in limestone

Quartz (possibly milky quartz)

Quartz (Silica; SiO₂)

Basalt Porphyry

Porphyritic Basalt

Agate

Silicon dioxide (Chalcedony), SiO2

Chert (specifically Jasper)

Silicon dioxide (SiO2) with iron oxide inclusions

Ironstone (Limonite/Goethite Concretion)

Ferruginous Sedimentary Rock (composed of Goethite FeO(OH) and Limonite)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Fossiliferous Limestone or Mudstone

Sedimentary Rock with Invertebrate Fossils

Weathered stone nodule or concretion

Unidentified lithic concretion; composition cannot be determined from the image

Basalt

Aphanitic Mafic Igneous Rock

Polymictic breccia, possibly volcanic breccia

Polymictic clastic breccia; likely a matrix-supported breccia containing lithic fragments, quartz, feldspar, and dark mafic minerals

Stromatolite

Laminated biogenic sedimentary structure (formed by Cyanobacteria)

Quartz Veined Rock (Likely Graywacke or Quartzite)

Silicon Dioxide (SiO2) veins in Metasedimentary matrix

Chert (or Flint)

SiO2 (predominantly microcrystalline quartz)

Chert Nodule (with Geode cavity)

Cryptocrystalline Quartz (SiO2)

Botryoidal chalcedony (possibly agate/geode material)

Chalcedony, microcrystalline quartz (SiO₂)

Weathered iron-rich sandstone or lateritic rock

Quartz-rich sandstone with iron-oxide cement; possibly ferruginous laterite

Ironstone concretion

Iron-oxide-cemented sediment, chiefly goethite (α-FeO(OH)) and/or hematite (Fe₂O₃)

Quartz Druze on Matrix (Geode Fragment)

Quartz (Silicon Dioxide, SiO2)

Pebble or Cobble (likely composed of sandstone or conglomerate)

Clastic Sedimentary Rock (specific name like sandstone, conglomerate, or breccia would require microscopic analysis of clast size and angularity)

Tumbled milky quartz (likely quartz/chalcedony)

Quartz, SiO₂; possibly microcrystalline chalcedony

Quartz geode

Microcrystalline and druzy quartz (SiO₂), likely chalcedony-lined

Porphyry (specifically Porphyritic Rhyolite or Andesite)

Porphyritic Igneous Rock (composed of Phenocrysts in an Aphanitic groundmass)

Marble

Recrystallized Calcite (CaCO3) or Dolomite (CaMg(CO3)2)

Jasper Conglomerate

Polymictic Conglomerate with Jasper and Quartz

Ocean Jasper

Orbicular Jasper (Silicon Dioxide, SiO2)

Tree Agate

Silicon Dioxide (SiO2) with Chlorite inclusions

Iron-rich weathered rock, likely lateritic sandstone or ironstone

Ferruginous sandstone/ironstone; chiefly quartz (SiO₂) with hematite/goethite (Fe₂O₃·nH₂O)

Crazy Lace Agate

Chalcedony (Silicon Dioxide, SiO2)

Celestine (or Celestite)

Strontium sulfate (SrSO4)

Sandstone (specifically Arkose or Siltstone variant)

Clastic Sedimentary Rock (primarily SiO2)

Amethyst geode fragment

Quartz, SiO₂; purple color from irradiation-related iron impurities

Chalcedony (Quartz)

Silicon dioxide (SiO2)

Agate Geode

Silicon Dioxide (SiO2) - Chalcedony / Quartz Variety

Chert (Jasper variety)

Microcrystalline Quartz (SiO2)

Dalmatian Jasper

Peralkaline Quartz-Feldspar Rock with Arfvedsonite

Crazy Lace Agate

Chalcedony (SiO2) with microcrystalline quartz

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Banded Gneiss

Gneiss (High-grade regional metamorphic rock)