Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Citrine Quartz

Silicon Dioxide (SiO2) with iron impurities

Turtle Stone / Septarian Nodule (Water-worn)

Septarian Concretion

Sandstone

Arenite (specifically Quartz Arenite)

Dark flint or chert fragment

Microcrystalline quartz (SiO₂), commonly called flint when dark and nodular

Wishing Stone (Basalt/Siltstone with Quartz/Calcite vein)

Carbonaceous Siltstone with Quartz (SiO2) or Calcite (CaCO3) vein

Amethyst

Silicon dioxide (SiO2) with iron impurities

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Botryoidal Hematite (Iron Stone Conglomerate)

Hematite (Fe2O3) in sedimentary matrix

Ironstone Concretion (Moqui Marble Type)

Goethite/Hematite-cemented Sandstone Concretion

Brown Jasper

Silicon Dioxide (SiO2) with iron oxide inclusions

Conglomerate

Polymictic Conglomerate

Calcite (or Alabaster, if truly carved)

Calcium Carbonate (CaCO3)

Not a rock, mineral, or geological specimen

Small rounded pebble

Indeterminate lithic grain; likely weathered sandstone, iron-stained quartz-rich rock, or a concretion

Pebble

Lithified rock fragment / Sedimentary clast

Weathered iron-rich rock, possibly basalt or ironstone

Uncertain; likely weathered basalt (plagioclase–pyroxene) or hematite/goethite-bearing ironstone

Chert

Silicon dioxide (SiO2)

Celestine

SrSO4

Dyed Blue Agate

Silicon Dioxide (SiO2) with artificial pigment

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Geode (Chert or Quartz Nodule)

Silicon Dioxide (SiO2)

Iron-rich weathered rock, likely lateritic sandstone or ironstone

Ferruginous sandstone/ironstone; chiefly quartz (SiO₂) with hematite/goethite (Fe₂O₃·nH₂O)

Unknown Rock Specimen

Limonite Concretion

Limonite (Hydrated iron(III) oxide-hydroxide) FeO(OH)·nH2O

Fossilized oyster or bivalve shell

Fossil Gryphaeidae or Ostreoidea; calcitic shell, CaCO₃

Septarian Nodule

Septarian Concretion (CaCO3 with Siderite/Limonite streaks)

Hag Stone

Perforated Sedimentary Rock / Flint / Limestone

Shale

Lutaceous Rock (Hydrous Aluminum Silicates)

Quartz Druzy Geode Fragment

Silicon Dioxide (SiO2)

Blue Chalcedony

Silicon Dioxide (SiO2)

Limestone (specifically Dolomitic/Crystalline Limestone)

Sedimentary Carbonate Rock (CaCO3 / CaMg(CO3)2)

Grooved Maun Ball (Maul/Hammerstone-like Concretion)

Calcareous/Ferruginous Concretion in Sandstone Matrix

Quartz (Druzy)

Silicon Dioxide (SiO2)

Geode with Quartz and Chalcedony

Silicon Dioxide (SiO2)

Weathered iron-rich rock, possibly laterite or ironstone

Goethite–hematite-rich ferruginous rock; uncertain without testing

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

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

Weathered quartz-rich rock, possibly sandstone or quartzite

Indeterminate; likely quartz sandstone (SiO₂-rich), possibly weakly metamorphosed quartzite

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

Limonite/goethite-rich ferruginous rock; exact identification requires testing

Limestone (Brecciated/Recrystallized)

Calcium Carbonate (CaCO3)

Ironstone Concretion

Siderite or Hematite-rich Concretion (FeCO3 / Fe2O3)

Picture Jasper

Silicon Dioxide (SiO2) with iron oxide and organic impurities