Ironstone Concretion / Limonite-stained Siltstone
Ironstone (primarily Limonite FeO(OH)·nH2O and Siltstone)
Category
Browse sedimentary (with some aspects of mineral replacement) specimens identified by the Rock Identifier community.
Ironstone Concretion / Limonite-stained Siltstone
Ironstone (primarily Limonite FeO(OH)·nH2O and Siltstone)
Chert (with Quartz Veining)
Microcrystalline Quartz (SiO2)
Sandstone Concretion
Clastic sedimentary rock (primarily Silica, SiO2, or Calcium Carbonate, CaCO3)
Petrified Wood
Silicified Wood (SiO2)
Chert (Jasper Variant likely)
Silicon Dioxide (SiO2)
Jasper
Jasper / Silicon Dioxide (SiO₂)
Ironstone Concretion (Iron-rich Mudstone)
Siderite / Geothite concretion (FeCO3 / FeO(OH))
Fuchsite Gneiss (Green Quartzite)
Chromium-rich Muscovite (KAl2(AlSi3O10)(OH)2 with Cr replacements)
Sandstone (Ferruginous)
Arenite (with high iron oxide content)
Gneiss
Gneiss
Chert (Common Opal variant)
Microcrystalline Quartz (SiO2)
Chert (Jasper/Flint variety)
Silicon dioxide (SiO2)
Chert (Flint Nodular Variety)
Microcrystalline Quartz (SiO2)
Chert (specifically Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Sandstone Concretion
Clastic Sedimentary Rock (primarily SiO2 with mineral cement)
Sandstone (likely Arkosic)
Clastic Sedimentary Rock
Sandstone
Sandstone (Sedimentary rock composed of silicate grains)
Chalcedony (specifically Agate or Common Opal variety)
Cryptocrystalline Silica (SiO2)
Sandstone
Arenite (SiO2 principal)
Chert (often called Flint in this context)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Black Sand (Magnetite Sand)
Magnetite-rich Placers (Fe3O4)
Chert (Nodule)
Silicon Dioxide (SiO2)
Green Banded Chert (Agate/Jasper)
Silicon Dioxide (SiO2) with trace impurities of Chlorite or Glauconite
Sandstone Concretion
Arenaceous concretion (primarily SiO2 with Fe2O3 staining)
Silty Shale
Silty Shale (Fissile Sedimentary Rock)
Chert (variant Flint or Jasper)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Chert (Chalcedony/Agate)
Microcrystalline Quartz (SiO2)
Chert (Nodule)
Silicon Dioxide (SiO2)
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Kambaba Jasper (Crocodile Jasper)
Stromatolitic Rhyolite/Jasper (SiO2)
Ferruginous Conglomerate (or Iron-Rich Concrete/Slag)
Clastic Sedimentary (Silicon Dioxide/Iron Oxide matrix)
Geode (Unopened)
Silica-rich concretion (SiO2)
Magnetite (Lodestone)
Magnetite (Fe3O4)
Pearl
Calcium Carbonate (CaCO3) with Conchiolin
Ironstone with Pyrite
Ferruginous Sandstone (Fe2O3) with minor Sulfide minerals (FeS2)
Quartz-veined Sedimentary Rock
Hydrothermally veined Clastic Sedimentary Rock (SiO2 veins in Matrix)
Chert (and Petrified Wood)
Silicon Dioxide (SiO2)
Chert (Yellow Jasper/Flint)
Silicon Dioxide (SiO2)
Gneiss (Banded Gneiss)
Gneiss
Agate
Agate (Silicon Dioxide - SiO2)
Fossil Coral
Fossilized Scleractinia or Tabulata (various genera/species)
Gneiss (with Quartzite and Biotite)
Gneiss containing SiO2 (Quartz), K(Mg,Fe)3AlSi3O10(OH)2 (Biotite), and (K,Na,Ca)AlSi3O8 (Feldspar)