Industrial Byproduct (Anthropogenic Rock Like Material)

Agate

Silicon Dioxide (Chalcedony), SiO2

Granite Cobble

Phaneritic Felsic Igneous Rock (Granite)

Banded Calcite (often sold as 'Travertine' or 'Mexican Onyx')

Calcium Carbonate (CaCO3)

Tiger’s eye

Quartz variety, primarily silicon dioxide (SiO₂); fibrous quartz pseudomorph after crocidolite asbestos

Diorite

Intermediate Phaneritic Igneous Rock (Diorite)

Red Sandstone

Arenite (Ferruginous Sandstone)

Sandstone

Sandstone (lithified arenite/wacke)

Boulder Opal

Hydrated Silica (SiO2·nH2O)

Granite Pebble

Phaneritic plutonic rock (Quartz, Feldspar, Mica)

Petrified Wood

Silicified Wood (SiO2)

Amethyst Quartz

Silicon Dioxide (SiO2)

Basalt

Basalt (Mafic Extrusive Igneous Rock)

Lapis Lazuli

Lapis Lazuli (Aggregate primarily of Lazurite: (Na,Ca)8(AlSiO4)6(S,SO4,Cl,1-2) with Calcite and Pyrite)

Granite

Granite (Phaneritic intrusive igneous rock)

Black Garnet (Melanite)

Andradite, Ca3Fe2(SiO4)3

Basalt with Weathering Rind

Basalt (Mafic Volcanic Rock)

River Pebble (Quartzite/Chert)

Quartzite with inclusions (SiO2)

Pink Granite

Phaneritic intrusive igneous rock with dominant Alkali Feldspar

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

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

Schist

Mica Schist (primarily Muscovite [KAl2(AlSi3O10)(OH)2] or Biotite)

Obsidian

Volcanic Glass (SiO2)

Garnet

Garnet Group (complex nesosilicates with general formula X3Y2(SiO4)3, where X can be Ca, Mg, Fe2+, Mn2+ and Y can be Al, Fe3+, Cr3+, V3+)

Petrified Wood

Silicified Wood (primarily Quartz/Chalcedony, SiO2)

Chert (Flint Nodule)

Microcrystalline Quartz (SiO2)

Quartz (Chalcedony / Rough Quartz Pebble)

Silicon Dioxide (SiO2)

Granitic Pebble (Glacial Erratic)

Granite

Granite Pebble (Salt and Pepper Granite)

Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Biotite/Amphibole)

Fossil Coral (Petoskey Stone or Chain Coral Pebble)

Hexagonaria percarinata / Rugosa coral (CaCO3)

Silicon

Element Si

Fulgurite

Fulgurite (Lechatelierite/Silica glass)

Limestone

Sedimentary Rock (Primarily Calcium Carbonate, CaCO3)

Amygdaloidal Basalt with Epidote

Amygdaloidal Basalt (Mafic volcanic rock)

Rough Corundum (likely Sapphire/Zircon-bearing)

Aluminium Oxide (Al2O3)

Granite

Granite

Chert (Yellow/Tan Jasper)

Microcrystalline Quartz (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Agate

Chalcedony (SiO2)

Conglomerate

Conglomerate (clastic sedimentary rock)

Limestone (River Pebble)

Calcium Carbonate (CaCO3)

Weathered basalt or other dark volcanic rock

Likely basalt; predominantly plagioclase feldspar and pyroxene, possibly olivine and iron oxides

Chert (specifically tan/pink variety)

Silicon Dioxide (SiO2)

Sandstone (Tumbled/River Pebble)

Arenite (composed primarily of SiO2)