Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Sandstone

Arenite (primarily SiO2)

Quartz geode

Microcrystalline and crystalline quartz (SiO₂), likely with minor chalcedony or calcite

Ironstone Concretion (Nutstone)

Ironstone (with High Limonite/Hematite Content)

Limonite/goethite-rich ironstone concretion (probable)

Goethite–limonite, chiefly FeO(OH)·nH₂O, possibly with hematite and manganese oxides

Quartz Geode

Silicon Dioxide (SiO2)

Quartz-rich breccia or vein quartz fragment

Quartz (SiO₂), likely with iron-oxide staining and attached host rock

Sandstone with Ironstone Concretion

Arenite with Ferruginous Cement

Quartz-rich rock fragment, possibly chalcedony or weathered quartz

Silicon dioxide (SiO₂), likely quartz/chalcedony

Basalt

Basalt

Geode (unopened)

Calcedony-lined Geode (SiO2)

Likely weathered limestone or calcareous concretion

Calcite-rich carbonate rock; chiefly calcium carbonate (CaCO₃)

Limonite / Ironstone Concretion

Hydrated Iron Oxide (FeO(OH)%C2%B7nH2O)

Citrine

Quartz (Silicon Dioxide - SiO2)

Quartz Geode / Druzy Quartz

Silicon Dioxide (SiO2)

Chalcedony (specifically Agate or Common Opal variety)

Cryptocrystalline Silica (SiO2)

Weathered iron-rich concretion or ironstone cobble

Goethite–hematite–limonite-rich ironstone; exact identification requires testing

Fluorite Geode

Calcium Fluoride (CaF2)

Sandstone (with secondary weathering/concretion)

Arenite (composed primarily of Quartz, SiO2)

Conglomeratic aggregate / pebble-rich concrete-like rock

Polymictic conglomerate (likely glacial or beach-derived gravel matrix); exact identification uncertain from image

Polished septarian nodule fragment

Septarian calcite–aragonite concretion, commonly with iron-rich minerals and possibly barite

Chert (Flint) with Limestone Matrix

Silicon Dioxide (SiO2) within Calcium Carbonate (CaCO3)

Pebble (river rock/beach pebble)

Pebble (clast size class)

Ironstone Concretion

Siderite or Hematite Concretion (FeCO3 or Fe2O3)

Ironstone Concretion (Boji Stone/Moqui Marble type)

Goethite/Hematite-encrusted Sandstone Concretion

Chert Concretion (with typical hematite/limonite staining)

Sedimentary Concretion (SiO2 with FeO(OH)⋅nH2O)

Quartz Geode

Silicon Dioxide (SiO2) in a Secondary Sedimentary/Volcanic cavity

Chert (or Flint)

Chert (cryptocrystalline quartz), SiO2

Druzy Quartz Geode

Silicon Dioxide (SiO2)

Blue-gray chalcedony geode with druzy quartz

Microcrystalline quartz (SiO₂), with quartz druse; possibly agate/chalcedony

Weathered sandstone pebble

Sandstone, composed primarily of quartz and feldspar grains cemented by silica, calcite, or iron oxides

Dalmation Jasper (or Dalmation Stone)

Dalmation Stone (composed of Perthite, Quartz, and Arfvedsonite)

Polished agate geode

Chalcedony (microcrystalline quartz, SiO₂) with quartz druse crystals

Quartz Geode

Silicon Dioxide (SiO2)

Ironstone concretion (likely hematite–limonite nodule)

Massive hematite (Fe₂O₃) and goethite/limonite (FeO(OH)·nH₂O), possibly an iron-rich concretion

Quartz geode or quartz-bearing rock

Quartz (SiO₂), likely in a chalcedony- or basalt-hosted cavity

Quartz (Druzy or Geode fragment)

Silicon Dioxide (SiO2)

Celestite (Blue Celestine)

Celestine (Strontium Sulfate, SrSO4)

Ironstone concretion

Iron-oxide-cemented sedimentary concretion, commonly hematite/goethite with quartz or clay

Quartz Geode

Crystalline Silicon Dioxide (SiO2) in Geode form

Ironstone (Limonitic Concretion)

Limonite (FeO(OH)·nH2O) with Goethite and Hematite inclusions

Ironstone Concretion (Boxwork)

Siderite-Limonite Concretion (FeO(OH)·nH2O)

Weathered iron-rich concretion or laterite fragment

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