Sedimentary (Chemically Precipitated Mineral)

Green Fluorite

Calcium Fluoride (CaF2)

Chalcedony Agate Nodule

Silicon Dioxide (SiO2)

Orange Calcite

Calcium Carbonate (CaCO3)

Banded Iron Formation (BIF)

Banded Iron Formation (Magnetite-Hematite-Chert)

Ferruginous Quartz on Ironstone

Silicon Dioxide (SiO2) with Hematite (Fe2O3)

Banded limestone or marble

Calcite-rich carbonate rock; likely veined limestone, possibly low-grade marble (CaCO₃)

Dyed Howlite (often sold as Turquenite)

Calcium Borosilicate Hydroxide (Ca2B5SiO9(OH)5)

Weathered quartz-rich pebble

Likely massive quartz (SiO₂), possibly quartzite or silicified rock

Green Fluorite

Fluorite (Calcium Fluoride, CaF2)

Dyed Agate Slice

Silicon Dioxide (SiO2) with artificial dyes

Banded calcite (likely cave deposit or vein fragment)

Calcite, CaCO₃

Chert or flint nodule

Microcrystalline quartz (SiO₂), likely chalcedony-rich chert

Ironstone Nodule

Ironstone (Ferruginous Rock)

Malachite

Copper Carbonate Hydroxide, Cu2CO3(OH)2

Banded Iron Formation (BIF)

Banded Iron Formation with Hematite and Jasper

Banded Iron Formation

Banded Iron Formation (BIF)

Liesegang Banded Sandstone (Concretion / Weathered Pebble)

Sandstone showing Liesegang rings / Weathering rind (SiO2 with iron oxides)

Ironstone (iron-rich sandstone or concretion)

Ferruginous sandstone, cemented by iron oxides/hydroxides such as hematite (Fe₂O₃) and goethite (FeO(OH))

Aragonite Star Cluster

Aragonite (Calcium Carbonate, CaCO3)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Quartz (Milky/Clear)

Silicon Dioxide (SiO2)

Chert (Flint / Agate Nodule)

Silicon Dioxide (SiO2)

Honey calcite (orange calcite)

Calcite, calcium carbonate (CaCO₃)

Calcite (honey calcite)

Calcite, calcium carbonate (CaCO₃)

Quartz vein in weathered host rock

Quartz (SiO₂), likely in a weathered metamorphic or igneous matrix

Milky quartz (rough quartz specimen)

Quartz, silicon dioxide (SiO₂)

Tumbled quartz (likely rose or milky quartz)

Quartz, silicon dioxide (SiO₂)

Banded Chert

Microcrystalline Quartz (SiO2)

Psilomelane (Black Hematite/Manganese Ore)

Barium Manganese Oxide (Formula: BaMn9O18(OH)4)

Blue Aragonite (polished)

Aragonite (CaCO3)

Pyrite-rich sulfide ore (likely pyrite with chalcopyrite)

Pyrite, FeS₂; possible chalcopyrite, CuFeS₂, and minor quartz or sphalerite

Quartz (Common or Milky)

Silicon Dioxide (SiO2)

Banded Calcite Onyx (Cave Onyx / Mexican Onyx)

Calcite (CaCO3) / Travertine

Light-colored limestone pebble

Calcite-rich limestone (primarily CaCO₃)

Banded iron formation (ironstone)

BIF; alternating hematite/magnetite and chert (SiO₂) layers

Green Chert

Microcrystalline Quartz (SiO2)

Eroded Limestone with Iron Staining

Carbonate Rock (CaCO3)

Chert (Iron-stained)

Microcrystalline Quartz (SiO2)

Pyrite in Quartz

Iron Sulfide in Silicon Dioxide (FeS2 + SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Septarian Nodule

Septarian Concretion (CaCO3 with Calcite/Aragonite and Clay/Mudstone)

Iron-rich concretion or weathered ironstone

Goethite–hematite limonite aggregate; commonly described as limonite or ironstone