Sedimentary (Chemically Precipitated)

Ironstone (Limonite/Hematite)

Ferruginous Sedimentary Rock (composed largely of Fe2O3 and FeO(OH)·nH2O)

Quartz Pebble

Silicon Dioxide (SiO2)

Banded Chert

Microcrystalline Quartz (SiO2)

Blue calcite (probable)

Calcite, calcium carbonate (CaCO₃)

Carnelian

Silicon Dioxide (SiO2) - variety of Chalcedony

Agate

Chalcedony (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Desert Rose (Gypsum Variety)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Orange Calcite (often commercially sold as Honey Calcite or Aragonite)

Calcium Carbonate (CaCO3)

Common Opal

Hydrated silica (SiO2 " nH2O)

Agate (specifically Waterline or Onyx-type Agate)

Silicon Dioxide (SiO2) - variety Chalcedony

Quartz

Quartz (Silicon Dioxide, SiO2)

Dark gray chert or flint nodule

Microcrystalline quartz (SiO₂), commonly chalcedony/quartz

Chert (Nodule)

Microcrystalline Quartz (SiO2)

Bog Iron (Limonite Concretion)

Limonite (FeO(OH)·nH2O)

Sandstone with Iron Staining

Arenite (SiO2 based with Fe2O3 staining)

Septarian Nodule

Septarian concretion (Complex mixture of Siderite/Limestone, Calcite, and Aragonite)

Quartz-veined Sedimentary Rock

Hydrothermally veined Clastic Sedimentary Rock (SiO2 veins in Matrix)

Chalcedony (likely common gray chalcedony)

Microcrystalline quartz, SiO₂

Carnelian

Silicon Dioxide (Quartz variety, SiO2)

Agate (specifically Carnelian Agate or Lake Superior style Agate)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Ironstone / Weathered Hematite

Iron oxide-rich sedimentary rock with Goethite/Hematite

Chert (specifically brown Chert or Jasper)

Microcrystalline Quartz (SiO2)

Limestone (River Pebble / Fossiliferous Limestone)

Calcium Carbonate (CaCO3)

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Banded Iron Formation

Banded Iron Formation (BIF)

Chert Pebble

Microcrystalline Quartz (SiO2)

Quartz-veined Siltstone/Greywacke

Clastic Sedimentary Rock with Quartz Infill (SiO2 vein)

Chert (Flint Nodules)

Cryptocrystalline Quartz (SiO2)

Ferruginous Sandstone with Concretion

Sandstone (SiO2 dominated with Fe2O3 cement)

Banded Iron Formation (Chert/Jasper)

Banded Iron Formation (BIF)

Limonite and Goethite encrusted Chert/Ironstone

Hydrated Iron Oxide (FeO(OH)·nH2O) with cryptocrystalline Silica (SiO2)

Quartz (Small Fragment)

Silicon Dioxide (SiO2)

Bauxite

Bauxite (Al(OH)3, AlO(OH))

Quartz pebble

Silicon dioxide (SiO2)

Veined Sandstone with Calcite Veins

Sedimentary sandstone with hydrothermal/mineral veins

Chert (Jasper variation)

Silicon dioxide (SiO2) - Microcrystalline Quartz

Limestone with Calcite Crust

Sedimentary Calcium Carbonate (CaCO3)

Oolitic Limestone

Oolite (Sedimentary Calcium Carbonate)

Oolitic Limestone

Oolite (Sedimentary Calcium Carbonate)

Heart-shaped Pebble (Limestone/Quartz)

Calcium Carbonate (CaCO3) / Silicon Dioxide (SiO2)

Jasper and Quartz Pebble

Silicon Dioxide (SiO2) microcrystalline quartz variety