Agate
Silicon dioxide (Chalcedony), SiO2
sedimentary
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Emerald (or possibly Green Glass / Slag)
Beryl (Be3Al2(SiO3)6)
gemstone
Sandstone with Manganese Staining
Quartz Arenite / Sedimentary Rock
sedimentary
Basalt
Extrusive Igneous Rock
igneous
Agate
SiO2 (Silicon dioxide, cryptocrystalline quartz variety chalcedony)
gemstone
White Quartz
Silicon Dioxide (SiO2)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Basalt Pebble
Extrusive Igneous Rock
igneous
Basalt
Mafic extrusive igneous rock
igneous
Hematite
Iron(III) oxide (Fe2O3)
mineral
Granite
Intrusive Igneous Rock
igneous
Scoria
Vesicular Mafic Extrusive Igneous Rock
igneous
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Quartz Pebble
Silicon Dioxide (SiO2)
sedimentary
Quartzite with Mafic Inclusions
Metamorphic Quartzite
metamorphic
Petrified Wood
Silicified Wood (SiO2)
fossil
Calcite
Calcium Carbonate (CaCO3)
mineral
Pyrite
Iron Sulfide (FeS2)
mineral
Greenstone
Metabasalt / Greenschist
metamorphic
Quartz Geode
Silicon Dioxide (SiO2)
sedimentary
Septarian Nodule with Calcite
Septarian Concretion (CaCO3 with internal calcite crystals)
sedimentary
Quartz Geode
Silicon Dioxide (SiO2)
mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Petoskey Stone
Hexagonaria percarinata
fossil
Basalt
Extrusive Igneous Rock
igneous
Septarian Nodule
Septarian Concretion (Calcite, Aragonite, and Limestone)
sedimentary
Quartzite
Metamorphic Quartz Sandstone
metamorphic
Lake Superior Agate
SiO2 (Quartz variety chalcedony)
gemstone
Crinoid Stem Fossil
Crinoid ossicle / stalk segment (Phylum Echinodermata)
fossil
Unakite
Granite (altered hydrothermal)
igneous
Crinoid Stem Fossil
Crinoid ossicle (Phylum Echinodermata)
fossil
Crinoid Stem Fossil
Crinoid columnal (Echinodermata)
fossil
Ferruginous Quartz / Iron-Stained Quartz
Silicon Dioxide with Iron Oxide impurities (SiO2 + Fe2O3)
mineral
Feldspar in Matrix
Feldspar group minerals in metamorphic or igneous matrix
igneous
Schist
Metamorphic rock (Schist)
metamorphic
Yellow Jasper
Quartz (Silicon Dioxide, SiO2 with impurities)
sedimentary
Agate
Silicon dioxide (Chalcedony), SiO2
sedimentary
Jasper
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Granite
Felsic intrusive igneous rock
igneous
Schist
Metamorphic Rock (Schist)
metamorphic
Agate
Silicon dioxide (Chalcedony), SiO2
sedimentary