Sedimentary (Chemically Precipitated)

Quartz Geode / Druzy Quartz

Silicon Dioxide (SiO2)

Red Jasper

Silicon Dioxide with Iron Oxide (SiO2)

Dyed Quartz Geode

Silicon Dioxide (SiO2) with artificial pigment

Chert (Field Stone)

Microcrystalline Quartz (SiO2)

Banded iron formation fragment

Banded iron formation (BIF), chiefly hematite/magnetite and chert (SiO₂)

Limonite (Ironstone)

Hydrated Iron(III) Oxide-hydroxide (FeO(OH)·nH2O)

Chert / Flint (with Crinoid Stem Molds)

Microcrystalline Quartz (SiO2)

Orange calcite

Calcite (calcium carbonate, CaCO₃)

Milky Quartz Vein in Host Rock

Silicon Dioxide (SiO2)

Likely ironstone concretion

Iron-oxide-cemented sedimentary concretion, commonly hematite/goethite-rich

Sandstone Cobble with Liesegang Rings

Arenite with iron oxide precipitation (SiO2 matrix with Fe2O3 banding)

Banded iron formation (ironstone)

Banded iron formation; chiefly hematite/magnetite (Fe₂O₃/Fe₃O₄) with chert (SiO₂)

Banded iron formation fragment (ironstone)

Banded iron formation; chiefly hematite/magnetite with chert (SiO₂)

Weathered limestone pebble

Limestone; predominantly calcite (CaCO₃)

Pink calcite cluster

Calcite (calcium carbonate, CaCO₃)

Calcite crystal cluster

Calcite — calcium carbonate, CaCO₃

Tumbled quartz-rich stone, likely marble or calcite

Calcite (CaCO₃), possibly marble

Hematite

Hematite (Fe2O3)

Ironstone pebble (likely limonite/goethite-rich)

Limonite, a mixture of hydrated iron oxides; commonly dominated by goethite (α-FeO(OH))

Quartz with Host Rock

SiO2 (Quartz) with fine-grained Matrix

Banded Iron Formation (BIF)

Banded Iron Formation (Taconite/Itabirite)

Oolitic Chert

Silicon Dioxide (SiO2) with oolitic texture

White quartz-rich rock, likely milky quartz or quartzite

Quartz (SiO₂); possibly quartzite, a metamorphosed quartz sandstone

Polished blue calcite

Calcite (CaCO₃), likely blue banded or massive calcite

Yellow Calcite

Calcium Carbonate (CaCO3)

Jasper

Microcrystalline Quartz (SiO2) with iron oxide impurities

Honey calcite (orange calcite)

Calcite, calcium carbonate (CaCO₃)

Pyrite nodule (probable iron sulfide concretion)

Pyrite, FeS₂, likely weathered within a sedimentary concretion

Orange Calcite

Calcite (Calcium Carbonate, CaCO3)

Orange Calcite

Calcite (Calcium Carbonate - CaCO3)

Green Calcite

Calcium Carbonate (CaCO3)

Orange Calcite

Calcium Carbonate (CaCO3)

Yellow Calcite

Calcium Carbonate (CaCO3)

Limestone Pebble

Calcite-rich Sedimentary Rock (CaCO3)

Likely pale green calcite

Calcite (calcium carbonate, CaCO₃)

Red calcite

Calcite (CaCO₃), likely iron- or manganese-colored

Calcite crystal cluster

Calcite (calcium carbonate, CaCO₃)

Iron-rich concretion or weathered ironstone pebble

Goethite–hematite-bearing limonite concretion (tentative)

Chert (Flint Nodules)

Silicon Dioxide (SiO2)

Red Jasper with Quartz Veining

Silicon Dioxide (SiO2) with Hematite impurities

Tumbled yellow calcite

Calcite (CaCO₃), likely honey/yellow calcite

Banded Iron Formation (BIF)

Banded Iron Formation (Magnetite-Hematite-Chert)