Sedimentary (Chemically Precipitated)

Weathered iron-rich rock, possibly laterite or limonite-bearing sandstone

Laterite/limonite-rich material; commonly dominated by goethite (FeO(OH)) and hydrated iron oxides

Ironstone Concretion / Goethite-Hematite Geode

Goethite / Hematite Concretion (Fe3O4 / FeO(OH) / Fe2O3)

Chert (Jasper)

Cryptocrystalline Quartz (SiO2)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chert (Flint)

Chert (Cryptocrystalline Silica/SiO2)

Chert (specifically Jasper or Flint type)

Microcrystalline Quartz (SiO2)

Boxwork Siderite or Sepatarian Nodule Weathering

Siderite (FeCO3) with secondary mineralization or Boxwork Geode fragment

Chert with Druzy Quartz Geode

Microcrystalline Quartz (SiO2)

Chert / River Jasper

Microcrystalline Quartz (SiO2)

Chert (variations include Flint or Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Flint variety)

Chert (SiO2)

Ironstone Concretion / Goethite Nodules

Ironstone (composed primarily of Goethite FeO(OH) and Limonite)

Chert (often called Flint when dark)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Jasper/Flint variety)

Microcrystalline quartz (SiO2)

Chert (Flint Nodular)

Chert (Silicon dioxide, SiO2)

Chert Nodule (Commonly known as Flint or River Rock)

Silicon Dioxide (SiO2)

Quartz

Silicon Dioxide (SiO2)

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

Limestone

Limestone (Calcium Carbonate: CaCO3)

Limestone Pebble

Limestone (Calcium Carbonate, CaCO3)

Limestone (Weathered)

Calcium Carbonate (CaCO3)

Limestone

Calcium Carbonate (CaCO3 / Calcite)

Rock salt (Halite)

Halite (Sodium Chloride, NaCl)

Limestone (River Pebble)

Calcite-rich Sedimentary Rock (CaCO3)

Bauxite (Laterite)

Hydrated aluminum oxides (Al2O3·nH2O)

Coal (likely Anthracite)

Anthracite coal

Sandstone with Liesegang Rings

Arenite with secondary Iron oxide (Limonite/Goethite) precipitation

Bauxite (Laterite Clay)

Bauxite (mixture of Hydrous Aluminum Oxides: Gibbsite Al(OH)3, Boehmite and Diaspore AlO(OH))

Limestone

Calcium Carbonate (CaCO3)

Chert

Sedimentary cryptocrystalline quartz (SiO2)

Red Jasper

Microcrystalline Quartz (SiO2) with iron oxide inclusions

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Chert (often called Flint)

Chert (SiO2)

Common Opal / Chert

Hydrated silica (SiO2·nH2O) or Microcrystalline Quartz (SiO2)

Quartz Sand Grain / Micro Crystal

Silicon Dioxide (SiO2)

Aragonite Star Cluster

Aragonite (CaCO3)

Chert

Microcrystalline Quartz (SiO2)

Quartz pebble

Silicon dioxide (SiO2)

Chert (Flint)

Chert (Cryptocrystalline Silica, SiO2)

Chert

Microcrystalline Quartz (SiO2)

Chert Pebble

Microcrystalline Quartz (SiO2)

Oolitic Limestone

Oolitic Carbonate (CaCO3)