Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Blue Chalcedony (likely dyed Agate)

Silicon Dioxide (SiO₂)

Sandstone concretion (Ironstone-stained)

Arenite with Limonite/Hematite staining (Silica-based with Iron Oxides)

Sandstone

Arenite (specifically Quartz Arenite)

Quartz Geode

Silicon Dioxide (SiO2)

Sandstone Chert Concretion

Silica-cemented Concretion (primarily SiO2)

Likely tumbled iron-stained quartz or chalcedony

Quartz/chalcedony (SiO₂), possibly limonite-coated

Aragonite / Calcite Geode

Calcium Carbonate (CaCO3)

Weathered iron-rich rock or concretion

Likely limonite/goethite-bearing concretion; exact identification requires testing

Quartz Geode (Unbroken)

Silicon Dioxide (SiO2)

Tumbled cream-colored stone, possibly calcite or quartz

Indeterminate from image; likely calcite (CaCO₃) or milky quartz (SiO₂)

Amethyst (Tumbled)

Amethyst (SiO2 with iron impurities)

Amethyst (Agate/Chalcedony variety)

Silicon Dioxide (SiO2) with iron impurities

Quartz Geode

Silicon Dioxide (SiO2)

Dyed Quartz Geode

Silicon Dioxide (SiO2) with artificial purple dye

Bumblebee Jasper

Volcanic Tuff (mixture of Quartz, Sulfur, Hematite, and Orpiment)

Satin Spar Selenite

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Septarian Nodule (Polished)

Septarian concretion (Calcite, Aragonite, Limestone)

Weathered sandstone or siltstone cobble

Clastic sedimentary rock, probably quartz-rich sandstone; exact identification requires testing

Weathered vesicular basalt (likely amygdaloidal basalt)

Basalt, composed mainly of plagioclase feldspar, pyroxene, and altered olivine; cavities may contain secondary zeolite, calcite, or silica

Iron-rich concretion or weathered ironstone

Limonite/goethite-rich ironstone; commonly hydrated iron oxides (FeO(OH)·nH₂O)

Weathered granite or granitic gneiss block

Granite, chiefly quartz, feldspar, and mica; possibly gneiss if the visible banding is structural

Iron-rich concretion or weathered ironstone

Goethite–hematite-rich limonite (FeO(OH)·nH₂O / Fe₂O₃)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Druzy Geode

Silicon Dioxide (SiO2) - Crystalline Variety

Sandstone (Ferruginous Concretion)

Ferruginous Sandstone Concretion / SiO2 with Fe2O3 cement

Chert (specifically Flint or Dark Chert)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Vesicular basalt (likely weathered volcanic rock)

Vesicular basalt; predominantly plagioclase, pyroxene, and possibly olivine, with secondary zeolite or calcite infill

Quartz Geode

Crystalline Silicon Dioxide (SiO2) within a nodule

Quartz (likely a weathered/tumbled piece)

Quartz (SiO₂)

Hag Stone

Perforated Sedimentary Rock / Flint / Limestone

Pebble

Lithified rock fragment / Sedimentary clast

Pink druzy quartz (possibly quartz-bearing calcite)

Quartz, SiO₂; the pale pink coloration may reflect iron impurities or included feldspar. Exact identification is uncertain from the image alone.

Druzy Quartz Geode (Partially Open)

Silicon Dioxide (SiO2) within Sedimentary Host Rock

Geode (Unopened)

SiO2 (Silicon Dioxide) - Chalcedony/Quartz Geode

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Quartz (Druzy)

Silicon Dioxide (SiO2)

Agate Geode Slice (with Druzy Quartz)

Silicon Dioxide (SiO2)

Quartz Geode Segment

Crystalline Silicon Dioxide (SiO2)

Quartz geode

Silica geode lined with microcrystalline quartz (SiO₂), possibly chalcedony

Quartz-rich breccia or vein quartz

Quartz (silicon dioxide, SiO₂), likely with iron-oxide staining and other pale gangue minerals

Chert / Flint Nodules in Sandstone

Microcrystalline Quartz (SiO2) within Clastic Sedimentary Rock

Limestone (specifically Dolomitic/Crystalline Limestone)

Sedimentary Carbonate Rock (CaCO3 / CaMg(CO3)2)