Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Druzy Quartz Geode (likely Smokey Quartz variety)

Silicon Dioxide (SiO2) - specifically a geode formation lined with druzy quartz crystals, with a likely brownish hue indicating smokey quartz.

Quartz Geode

Crystalline Silicon Dioxide (SiO2) in Geode form

Sandstone Concretion

Arenaceous concretion (primarily SiO2 with Fe2O3 staining)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2) - Crystalline Quartz

Ironstone (Limonite/Hematite)

Ferruginous sedimentary rock (Fe2O3·nH2O / Fe2O3)

Gneiss (specifically Granite Gneiss)

Gneiss (High-grade Regional Metamorphic Rock)

Sandstone with Ironstone Concretion

Arenite with Hematite/Goethite nodules (Fe2O3 / FeO(OH))

Weathered sandstone or iron-stained sedimentary rock

Quartz-rich clastic sandstone; exact identification requires testing

Puddingstone (Quartzite Conglomerate with Jasper inclusions)

Metaconglomerate (Silicon Dioxide, SiO2)

Agate (specifically Botswana or Lake Superior style chalcedony)

Silicon Dioxide (SiO2)

Citrine Geode

Silicon Dioxide (Quartz variety, often heat-treated amethyst): SiO2

Quartz geode

Quartz (SiO₂), lining a geode cavity; likely with minor iron-oxide staining

Quartz Geode

Silicon Dioxide (SiO2)

Sandstone (with Iron Siderite Concretion)

Arenite with Ironstone Concretion (FeCO3)

Quartz Geode

Silicon Dioxide (SiO2)

Dalmatian Stone

Peralkaline rhyolite

Petrified Wood

Silicified Wood (SiO2)

Gneiss (specifically Pink Gneiss)

Gneiss (high-grade regional metamorphic rock)

Weathered iron-rich mineral concretion

Likely limonite/goethite concretion (hydrated iron oxides), possibly a weathered ironstone fragment

Quartz Geode

Silicon Dioxide (SiO2)

Concretion with Quartz Veining

Septarian Concretion (CaCO3 / SiO2)

Basalt with Vesicle/Vug

Basalt (Aphanitic Mafic Igneous Rock)

Vesicular basalt (possibly weathered amygdaloidal basalt)

Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine, with weathering minerals filling vesicles

Conglomerate (Puddingstone)

Conglomerate (specifically, clastic sedimentary rock)

Rounded ironstone or weathered basalt pebble

Likely basaltic rock, possibly iron-rich concretion; exact identification requires testing

Quartz Geode in Sedimentary Host Rock

Silicon Dioxide (SiO2) in Carbonate Matrix

Quartz Geode

Silicon Dioxide (SiO2)

Basalt

Basalt (composition predominately plagioclase feldspar and pyroxene)

Basalt

Mafic volcanic rock

Botryoidal chalcedony (possibly agate/geode material)

Microcrystalline quartz, SiO₂; commonly chalcedony with quartz-lined cavities and iron-oxide staining

Agate (specifically a Blue Agate Geode Slice)

Chalcedony (cryptocrystalline variety of Quartz); SiO2

Quartz Geode

Silicon Dioxide (SiO2) in a Sedimentary Vug

Quartz Geode

Crystalline Silicon Dioxide (SiO2)

Amethyst Geode

Quartz (Silicon Dioxide, SiO2) with iron impurities

Basalt (Vesicular/Scoria)

Basalt (Extrusive Mafic Rock)

Quartz (likely Herkimer Diamond style)

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz-rich stone, possibly calcite or quartz

Likely quartz (SiO₂) or calcite (CaCO₃); exact identification requires testing

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Geode (Unopened)

Chalcedony/Quartz Geode (SiO2)