Geode or Concretion
Silica-based Concretion / Quartz Geode
sedimentary
Category
Not A Rock
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Ferruginous Sandstone
Clastic sedimentary rock (SiO2 with Fe2O3/FeO(OH) cement)
sedimentary
Granite
Granite (Felsic Plutonic Rock)
igneous
Granite
Granite (Felsic Plutonic Rock)
igneous
Sandstone
Arenite (primarily SiO2)
sedimentary
Quartzite
Quartzite (SiO2)
metamorphic
Chert (Jasper/Chalcedony)
Microcrystalline Quartz (SiO2)
sedimentary
Carnelian Agate
Silicon Dioxide (SiO2) - variety of Chalcedony
mineral
Obsidian
Obsidian (Volcanic Glass)
igneous
Red Jasper with Quartz
Microcrystalline Quartz (SiO2) with Hematite inclusions
sedimentary
Quartz / Rose Quartz
Silicon Dioxide (SiO2)
mineral
Quartz (Iron-Stained)
Silicon Dioxide (SiO2)
mineral
Chert (Common Opal/Agate variety)
Microcrystalline Quartz (SiO2)
sedimentary
Quartz Geode
Silicon Dioxide (SiO2)
mineral
Sandstone
Arenite (SiO2 predominantly)
sedimentary
Opal
Hydrated Silica (SiO2·nH2O)
mineraloid
Granite
Granite (Mainly Quartz, Alkali Feldspar, and Plagioclase)
igneous
Opal
Hydrated Silica (SiO2·nH2O)
mineral
Laterite (Iron-rich bauxite or Gossan)
Ferricrete (Fe2O3·nH2O)
sedimentary
Quartzite
Quartzite (composed primarily of SiO2)
metamorphic
Geode (Unopened)
Chalcedony/Quartz Geode (SiO2)
sedimentary
Biotite Mica
Biotite (K(Mg,Fe)3AlSi3O10(OH,F)2)
mineral
Chert (Flint)
Microcrystalline Quartz (SiO2)
sedimentary
Undetermined Due to Blur (Possible Flesh-Tone Mineral)
Unknown (Insufficient Visual Clarity)
Mineral
Sandstone
Arenite
sedimentary
Botryoidal Quartz / Calcite Geode crust
Silicon Dioxide (SiO2) or Calcium Carbonate (CaCO3)
mineral
Mookaite Jasper
SiO2
Sedimentary
Unakite
Unakite (Epidotized Granite)
metamorphic
Sandstone
Arenite (SiO2 primarily)
sedimentary
Herkimer Diamond in Matrix
Quartz (SiO2) in Dolostone (CaMg(CO3)2)
sedimentary (host) / mineral (crystals)
Sandstone
Arenite (SiO2 based)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Quartz Pebble
Crystalline Silicon Dioxide (SiO2)
sedimentary
Chert (or Flint)
SiO2 (Microcrystalline Quartz)
sedimentary
Sandstone
Arenite (SiO2 based)
sedimentary
Sodalite
Sodalite (Na8Al6Si6O24Cl2)
mineral
Sandstone
Arenite
sedimentary
Chert
Microcrystalline Quartz (SiO2)
sedimentary
Septarian Nodule (Dragon Stone)
Calcite-Aragonite-Limestone Septarian
sedimentary
Sandstone (Ferruginous)
Arenite (primarily SiO2 with Fe2O3 staining)
sedimentary
Red Jasper (possibly with Agate inclusions)
Silicon Dioxide (SiO2)
sedimentary
Jasper
Jasper (Silicon Dioxide, SiO2)
sedimentary