Sedimentary (Secondary Formation)

Milky Quartz Pebble

Silicon Dioxide (SiO2)

Sandstone Concretion with Fossil Wood

Ferruginous Sandstone Concretion (SiO2 with Fe2O3 cement)

Quartz-rich rock, possibly milky quartz

Quartz (SiO₂); the photo may show a quartz-rich rock, but its texture is not clear enough to determine a specific rock name.

Rounded sandstone pebble

Quartz-rich sandstone (composition cannot be confirmed from the image)

Small brown pebble, possibly chert or jasper

Undetermined silica-rich pebble; possibly microcrystalline quartz (SiO₂)

Chert (likely a small flake)

Microcrystalline quartz (SiO₂); the flake-like shape alone does not establish whether it is naturally fractured or worked

Fine-grained gray-green pebble

Likely lithic sandstone or siltstone; exact identification is not possible from the image alone

Weathered mica-rich rock fragment

Likely mica schist or phyllite; identification is uncertain from the image alone

Weathered rock pebble, possibly quartz-rich sandstone

Uncertain from the image; likely quartz-bearing sandstone with iron-oxide staining

Specular hematite (likely iron-rich ore)

Hematite, Fe₂O₃; possibly magnetite-bearing

Tumbled metallic-gray stone, likely hematite or magnetite

Hematite (Fe₂O₃) or magnetite (Fe₃O₄); exact identification requires testing

Rounded river pebble, likely altered limestone or sandstone

Probable micritic limestone (calcite-rich, CaCO₃) or fine-grained sandstone

Small rounded pebble, likely sandstone or weathered limestone

Indeterminate clastic carbonate/siliciclastic pebble; mineral composition appears dominated by quartz, feldspar, and/or calcite

Red Jasper Pebble

Opaque microcrystalline Quartz (SiO2) with Iron Oxide

Light-colored pebble, likely quartzite or weathered limestone

Indeterminate from image; possible quartzite (microcrystalline SiO₂)

Red Jasper

Silicon Dioxide (SiO2) with Hematite impurities

Red Jasper (with Hematite inclusions)

Silicon Dioxide (SiO2) with Iron Oxide (Fe2O3)

Flexicalymene Trilobite Fossil

Flexicalymene meeki (Order Phacopida, Family Calymenidae)

Red Jasper (Chert)

Silicon Dioxide (SiO2) with iron oxide inclusions

Carnelian

Chalcedony (SiO2)

Red Jasper

Silicon Dioxide (SiO2) with iron oxide inclusions

Chalcedony Geode Fragment

Microcrystalline Quartz (SiO2)

Red Jasper

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

Red Jasper

Silicon Dioxide (SiO2) with Iron inclusions

Mixed River Stones and Agates

Mixed Silicates and Ironstones (primarily SiO2 and Fe2O3)

Chert (Common Opal variant)

Silicon Dioxide (SiO2)

Geode Nodules / Keokuk Geode

Quartz / Chalcedony Geode (SiO2)

Brecciated Jasper

Microcrystalline Quartz (SiO2)

Chert (containing Orbicular/Agate patterns)

Microcrystalline Quartz (SiO2)

Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

Quartz-veined Sandstone Pebble

Quartzose Sandstone with Quartz Veinlets

Exposed shoreline bedrock and sediment

Unidentified natural rock; the image does not show enough detail for a specific geological identification

Weathered iron-rich rock (likely ironstone or limonite-bearing concretion)

Goethite–hematite–limonite mixture, commonly written FeO(OH) ± Fe₂O₃

Turquoise

Turquoise — hydrated copper aluminum phosphate, CuAl₆(PO₄)₄(OH)₈·4H₂O

Turquoise

Hydrous phosphate of copper and aluminium (CuAl6(PO4)4(OH)8·4H2O)

Rhodochrosite

Manganese Carbonate (MnCO3)

Snakeskin Agate

Agate (Cryptocrystalline Quartz, SiO2)

Turquoise

Hydrated phosphate of copper and aluminium [CuAl6(PO4)4(OH)8·4H2O]

Ferruginous Quartz

Silicon Dioxide (SiO2) with Hematite/Limonite impurities

Turquoise

Hydrated copper and aluminum phosphate (CuAl6(PO4)4(OH)8·4H2O)

Turquoise (Rough Specimens)

Hydrous phosphate of copper and aluminium - CuAl6(PO4)4(OH)8·4H2O