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Chert (often called Flint when dark)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Amber Agate / Carnelian

Chalcedony (Silicon Dioxide, SiO2)

Red Ochre (Hematite-rich Clay)

Limonitic/Hematitic Claystone (Fe2O3 with clay minerals)

Granite

Plutonic Igneous Rock (composed typically of SiO2, Al2O3, K2O, Na2O, CaO)

Carnelian Agate

Silicon Dioxide (SiO2) - variety of Chalcedony

Chert Pebble/Nodule

Chert (a microcrystalline or cryptocrystalline sedimentary form of quartz, SiO2)

Quartzite

Quartzite (SiO2)

Banded Gneiss (with possible weathered sulfide or iron staining)

Gneiss, potentially with iron oxide/hydroxide staining (e.g., limonite) or weathered sulfides

Biotite Schist

Biotite Schist (Rich in K(Mg,Fe)3AlSi3O10(OH)2)

Greisen (Quartz-Muscovite-Turretine Rock)

Greisen

Biotite Schist with Garnet

Garnet-Biotite Schist

Dyed Howlite (simulating Lavender/Purple Jade or Charoite)

Howlite: Ca2B5SiO9(OH)5 (when natural)

Tumbled Carnelian and Quartz Mix

Silicon Dioxide (SiO2) with iron oxide impurities

Gneiss

Gneiss (High-grade Metamorphic Rock)

Carnelian

Carnelian Chalcedony (SiO2 with Iron Oxide impurities)

Gneiss

Gneissic Metamorphic Rock

Carnelian Agate

Silicon Dioxide (SiO2)

Sandstone (Weathered)

Arenite (primarily SiO2)

Eye Agate

Silicon Dioxide (SiO2) - Banded Chalcedony

Massive Quartz with Host Rock

Silicon Dioxide (SiO2)

Chert (and Limestone) River Cobble

Microcrystalline Quartz (SiO2) within Calcium Carbonate (CaCO3)

Petrified Wood

Silicified Wood (SiO2)

Carnelian

Carnelian (SiO2 with Iron Oxide impurities)

Limonite (Iron Ore)

Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)

Granite Cobble

Felsic intrusive igneous rock (composition: SiO₂ with KAlSi₃O₈, NaAlSi₃O₈, and CaAl₂Si₂O₈)

Carnelian (Red Chalcedony)

Silicon Dioxide (SiO2)

Carnelian (Chalcedony)

Silicon Dioxide (SiO2)

Milky Quartz (Gold-bearing Prospecting Specimen)

Silicon Dioxide (SiO2)

Quartz

Silicon Dioxide (SiO₂)

Quartz (Milky Quartz vein fragment)

Silicon Dioxide (SiO2)

Folded Schist / Gneiss (Metamorphic Rock)

Regional Metaphoric Folded Outcrop (predominantly Schist/Gneiss)

Granitic Gneiss

Gneiss (Polymetamorphic Granitic Gneiss)

Basalt (Arrowhead form)

Extrusive mafic igneous rock

Sandstone with Iron Concretion

Arenite with Limonite/Goethite Concretion

Banded Agate (specifically Sardonyx Agate)

Silicon Dioxide (SiO2) - Chalcedony variety

Carnelian Agate

Chalcedony (SiO2 with iron oxide impurities)

Chalcedony in Host Rock

Chalcedony (SiO2)

Carnelian (Chalcedony)

Cryptocrystalline Quartz (SiO2) with Iron Oxide impurities

Quartz

Quartz (SiO2 - Silicon Dioxide)

Anthracite Coal

Low-grade metamorphic carbonaceous rock

Quartz in Host Rock

Silicon Dioxide (SiO2) in Rhyolite or Granite matrix

Dendritic Limestone

Calcite with Manganese Oxide (Manganese Dendrites)