Not A Rock (Synthetic Material)

Orbicular rhyolite (likely)

Rhyolite, a silica-rich volcanic rock; commonly quartz, alkali feldspar, plagioclase, and iron-rich alteration minerals

Fossiliferous Limestone / Petrifaction

Sedimentary rock with fossil inclusions / Calcium Carbonate (CaCO3)

Sandstone (Red Sandstone)

Clastic Sedimentary Rock (primarily SiO2 with Iron Oxide)

Quartz Pebble

Silicon Dioxide (SiO2)

Quartz-rich metamorphic rock, likely quartzite

Quartzite; predominantly quartz (SiO₂), with minor iron-oxide and mica impurities

Quartzite Cobble

Metamorphosed Quartz Sandstone (SiO2)

Weathered quartz-rich rock, likely silicified limestone or quartzite

Microcrystalline quartz (SiO₂), possibly with calcite (CaCO₃) and iron-oxide staining

Quartz-bearing granite or gneiss fragment

Granite/gneiss composed mainly of quartz (SiO₂), feldspar, and minor mica or ferromagnesian minerals

Obsidian

Obsidian (principally SiO2)

Man-made Metal Pin (Non-geological)

Antimony-Lead Alloy or Zinc/Brass Base with Electroplating

Sandstone (Water-worn)

Arenite

Tumbled blue-green stone, likely aquamarine-bearing pegmatite or blue apatite

Probable fluorapatite, Ca5(PO4)3(F,Cl,OH), though visual identification is uncertain

Jasper

Silicon dioxide (SiO2) with impurities

River Rock (Quartzite Pebble)

Quartzite (primarily SiO2)

Red Sandstone

Arenite (primarily Quartz with Hematite cement)

Fossiliferous limestone

Bioclastic carbonate rock, primarily calcite (CaCO₃)

Sandstone (Ferruginous)

Clastic sedimentary rock (primarily SiO2 with Fe2O3)

Banded Agate (specifically Carnelian Agate)

Silicon dioxide (SiO2) - Chalcedony variety

Chert (Chalcedony/Agate)

Microcrystalline Quartz (SiO2)

Vesicular quartz-rich rock, possibly weathered rhyolite or hydrothermal quartz

Likely quartz (SiO₂) with altered feldspar, iron oxides, and cavities; exact identification requires testing

Banded Chert / Sandstone Pebble

Microcrystalline Quartz (SiO2) / Silicified Sandstone

Weathered quartz-rich rock, possibly granite or pegmatite fragment

Uncertain; likely quartz–feldspar aggregate, potentially granitic pegmatite

Tumbled gray-green metamorphic rock, likely serpentinite or chlorite schist

Serpentinite/chlorite-rich ultramafic metamorphic rock; commonly dominated by antigorite, lizardite, or chlorite with minor magnetite and talc

Tumbled carnelian agate with dark mineral inclusions

Carnelian, an orange variety of microcrystalline quartz (chalcedony), SiO₂; dark inclusions are likely iron oxides/hydroxides, possibly hematite, goethite, or a basaltic/matrix fragment

Likely weathered quartz-bearing rock fragment

Indeterminate; appears to contain quartz (SiO₂) with iron-oxide staining, possibly from quartzite, granite, or pegmatite

Chert (Agatized/Banded)

Chert (Microcrystalline Silicon Dioxide, SiO2)

Conglomerate

Clast-supported polymict conglomerate

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Banded Chert

Microcrystalline Quartz (SiO2)

Gneiss

Gneiss (quartz-feldspar-biotite gneiss)

Slag

Ferrous Slag (Amorphous calcium-magnesium-aluminum silicates)

Dyed Agate

Silicon Dioxide (SiO2) - variety Chalcedony

Obsidian with Slate/Tuff

Volcanic glass (SiO2) with associated pyroclastic rock

Granodiorite Pebble

Granodiorite (containing Quartz, Plagioclase Feldspar, and Biotite/Amphibole)

Iron-rich laterite or limonite/goethite-bearing rock

Hydrated iron oxides, chiefly goethite (α-FeO(OH)) and limonite (FeO(OH)·nH₂O), likely in a lateritic matrix

Chert (Nodule/Pebble)

Chert (Silicon Dioxide, SiO2)

Granite

Phaneritic plutonic rock (SiO2 rich)

Granite (specifically Rapakivi Granite)

Phaneritic Felsic Igneous Rock (Granite)

Red jasper (iron-rich chalcedony), possibly brecciated

Jasper: microcrystalline quartz, SiO₂, colored mainly by iron oxides/hydroxides

Chert Pebble

Chert (composed primarily of Microcrystalline Quartz, SiO2)

Mookaite Jasper

Silicified Radiolarite (SiO2)

Iron-rich breccia (likely hematite–goethite breccia)

Hematite (Fe₂O₃) and goethite (FeO(OH)) in a silicified or iron-cemented breccia