Sedimentary (Chemically Precipitated)

Quartz Geode (Druzy Quartz)

Silicon Dioxide (SiO2)

Likely quartz-rich rock fragment

Probably microcrystalline quartz (SiO₂), possibly a pale chert or quartzite fragment

Orange calcite

Calcite, calcium carbonate (CaCO₃)

Limonite (Iron Ore/Bog Iron)

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

Limestone

Calcium Carbonate (CaCO3)

Banded Iron Formation (BIF) / Ironstone

Magnetite-Hematite Quartzite / Ironstone

Sandstone with Iron Staining

Clastic sedimentary rock (SiO2 with iron oxides)

Limestone (or Calcite Nodules)

Calcium Carbonate (CaCO3)

Banded Flint (Chert)

Silicon Dioxide (SiO2)

Iron-oxide-rich breccia or weathered ironstone

Hematite–goethite ironstone, likely brecciated and quartz-bearing

Iron-rich concretion or weathered ironstone pebble

Goethite/limonite-bearing ironstone; commonly an iron-oxide concretion (FeO(OH)·nH₂O, variable)

Yellow Ocher (Limonite)

Limonite (Hydrated Iron Oxide) - FeO(OH)·nH2O

Calcite crystal specimen

Calcite — calcium carbonate, CaCO₃

Microcrystalline Limestone

Limestone (CaCO3 with impurities)

Honey calcite crystal fragment

Calcite (CaCO₃), likely honey or amber calcite

Celadonite in Basalt (Green Earth)

Celadonite (K(Mg,Fe2+)(Fe3+,Al)Si4O10(OH)2)

Orange calcite

Calcite (calcium carbonate, CaCO₃)

Jasper with Hematite

Silicon Dioxide (SiO2) with Ferric Oxide (Fe2O3)

Ocean Jasper

Orbicular Jasper (Silicon Dioxide, SiO2)

Weathered iron-rich concretion or laterite fragment

Ferruginous concretion, likely goethite/limonite (hydrated iron oxides) in a clay-rich matrix

Quartz vein specimen

Quartz (SiO₂), likely drusy or massive quartz on host rock

Hematite

Iron(III) oxide (Fe2O3)

Dolomite on Prehnite (Saddle-shaped Dolomite)

Dolomite [CaMg(CO3)2] on Prehnite [Ca2Al(AlSi3O10)(OH)2]

Jasper (Iron-stained Chert)

Silicon Dioxide (SiO2) with Iron Oxides

Chert (Jasper / Petrified Wood)

Microcrystalline Quartz (SiO2)

Jasper with Quartz Druzy

Silicon Dioxide (SiO2)

Blue-green calcite

Calcite (CaCO₃), likely copper-bearing or otherwise inclusions-colored

Banded Iron Formation (Fragment)

Banded Iron Formation (BIF)

Tumbled honey calcite

Calcite (calcium carbonate, CaCO₃)

Limestone

Calcium Carbonate (CaCO3)

Chalcedony (Agate / Quartz Geode Fragment)

Silicon Dioxide (SiO2)

Weathered ironstone concretion (possible hematite/goethite concretion)

Hematite–goethite-rich ferruginous concretion; primarily Fe₂O₃ and FeO(OH) in a silica/clay matrix

Chert on Volcanic Host Rock

Sedimentary Chert (SiO2) within Basalt or Andesite

Moqui Marble (Sandstone Concretion)

Hematite-cemented Sandstone (Fe2O3 + SiO2)

Septarian Nodule

Septarian Concretion (CaCO3 with Siderite/Calcite)

Quartz / Common Opal Transition

Silicon Dioxide (SiO2)

Quartz / Quartzite

Silicon Dioxide (SiO2)

Likely iron-rich metamorphic rock (possibly hematite-rich ironstone)

Uncertain from the image; possible hematite-bearing ironstone, chiefly Fe₂O₃ with associated silicate minerals

Limonite

FeO(OH)·nH2O

Moqui Marble (Shaman Stone)

Ironstone Concretion (Goethite/Hematite Shell)

Weathered limestone

Calcite-rich limestone (predominantly CaCO₃)

Sandstone (Ferruginous)

Arenite (Fe-rich SiO2)