Rock (Likely Sedimentary)

Chert Nodules in Limestone

Microcrystalline Quartz (SiO2) within Calcium Carbonate (CaCO3)

Rounded river pebble, likely quartz-rich sandstone or fine-grained granite

Indeterminate from photograph; possible quartz/feldspar-bearing granitic pebble

Fluorite on Matrix

Calcium Fluoride (CaF2)

Fluorite Geode

Calcium Fluoride (CaF2)

Sandstone (specifically Flagstone)

Arenite (primarily composed of SiO2)

Sandstone (likely Graywacke or Arkosic varieties)

Arenite (composed primarily of SiO2)

Weathered iron-rich rock, likely hematite–goethite-bearing basalt or ironstone

Basalt/ironstone matrix with hematite (Fe₂O₃), goethite [FeO(OH)], and possibly limonite

Rounded gray river pebble, likely fine-grained sandstone or siltstone

Indeterminate clastic sedimentary rock; possibly quartz-rich sandstone or siltstone

Granite-like rock

Coarse-grained granitoid, likely granite or granodiorite

Likely weathered sandstone or iron-stained sedimentary rock

Quartz-rich sandstone; exact identification is limited by the blurred photograph

Weathered basalt or mafic volcanic rock

Basalt; typically plagioclase feldspar, clinopyroxene, and often olivine or iron oxides

Quartz (Iron-Stained)

Silicon Dioxide (SiO2)

Dark weathered metamorphic rock, likely schist or phyllite

Undetermined; probably mica-rich quartz–feldspar schist/phyllite

Pink granite or granitic gneiss

Coarse-grained quartz–feldspar–mica rock; likely granite, possibly weathered gneiss

Quartz Vein in Host Rock (clastic sediment)

Silicon Dioxide (SiO2) in matrix

Tumbled fossiliferous limestone (likely fossiliferous marble)

Fossiliferous limestone, composed mainly of calcite (CaCO₃); the pale circular fossils appear to be shell or crinoid fragments

River Pebble (Likely Chert or Fine-Grained Sandstone/Quartzite)

Siliciclastic clast (likely Chert or Quartzarenite/Quartzite pebble)

Weathered schist or gneiss

Quartz–feldspar–mica metamorphic rock

Chert Nodule (Commonly known as Flint or River Rock)

Silicon Dioxide (SiO2)

Felsic Drill Core (likely Gneiss or Granite)

Felsic Metamorphic Rock (Gneissic profile)

Weathered granite pebble

Granite, typically quartz + feldspar + mica; approximate composition varies

Banded metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss, possibly migmatitic

Likely gray sandstone or fine-grained metamorphic rock

Quartz-rich lithic sandstone; exact identification is uncertain from the photograph

Iron-stained chert or weathered ironstone nodule

Microcrystalline quartz (SiO₂), possibly limonite/goethite-bearing

Weathered granite or granitic gneiss

Granite; chiefly quartz, feldspar, and biotite/hornblende

Sandstone (Quartzite-rich Pebble)

Arenite (composed primarily of SiO2)

Weathered granite or granitic gneiss cobble

Granite; mainly quartz, feldspar, and mica (exact identification is limited by the photograph)

Likely pale limestone or calcite-rich rock

Calcite-bearing limestone; chiefly calcium carbonate (CaCO₃)

Weathered iron-rich sandstone or ironstone cobble

Ferruginous sandstone/ironstone, chiefly quartz (SiO₂) cemented or stained by iron oxides and hydroxides

Sandstone (likely Greywacke variant)

Arenite

Tumbled beige stone, possibly quartz or calcite

Indeterminate from photograph; likely microcrystalline quartz (SiO₂) or calcite (CaCO₃)

Hard Sandstone (Quartzite)

Quartz-rich Sedimentary Rock (Proto-Quartzite)

Weathered brown stone, possibly mudstone or iron-stained limestone

Indeterminate sedimentary rock; likely clay-rich mudstone/shale or ferruginous limestone

Weathered iron-rich sandstone or laterite

Ferruginous sandstone; chiefly quartz (SiO₂) cemented by iron oxides/hydroxides

Geode (Unopened)

Siliceous Septarian Concretion / Geode (SiO2)

Polished banded agate (likely carnelian/black agate)

Microcrystalline quartz, SiO₂ (chalcedony/agate)

Rounded quartz-rich river pebble

Likely quartz arenite or chert-derived sandstone; identification is limited from the photograph

Likely weathered quartz-rich rock fragment

Uncertain; possibly quartz sandstone or a pale feldspathic rock

Basalt and Quartz Pebble

Basalt (Igneous) and Quartzite/Quartz (SiO2) pebble

Tumbled jasper or chalcedony

Microcrystalline quartz (SiO₂), likely jasper/chalcedony

Quartz Pebble

Crystalline Silica (SiO2)

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

Goethite–hematite (FeO(OH)–Fe₂O₃) in a silicate-rich matrix; exact identification requires testing