Chert (Flint)
Chert (Microcrystalline or cryptocrystalline Quartz, SiO2)
sedimentary
Category
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Unakite
Epidotized Granite
metamorphic
Amygdaloidal Basalt with Epidote
Amygdaloidal Basalt (Mafic volcanic rock)
igneous
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Rounded granite pebble
Granite; chiefly quartz, feldspar, and mica
igneous
Sandstone (lithic wacke/arenite)
Clastic sedimentary rock (SiO2 + varied clasts)
sedimentary
River Cobble (Basaltic/Andesitic)
Mafic Igneous Porphyritic Rock
igneous
Unidentified coarse-grained rock fragments
Likely granite or granitic rock; exact identification is uncertain from the photograph
igneous
Chert (Flint variety)
Chert (SiO2)
sedimentary
Yellow quartz, possibly citrine
Quartz (SiO₂), yellow variety likely citrine; may also be iron-stained quartz
mineral
Basalt
Basalt (extrusive igneous rock)
Igneous
Milky quartz with iron-oxide staining
Quartz (silicon dioxide, SiO₂)
mineral
Chert (River Pebble)
Microcrystalline Quartz (SiO2)
sedimentary
Ferruginous Quartzite (Red Sandstone/Quartzite)
Quartzite with Iron inclusions (SiO2 + Fe2O3)
metamorphic
Quartz (Milky or Clear variety)
Silicon Dioxide (SiO2)
mineral
Sandstone (Ferruginous)
Clastic Sedimentary Rock (SiO2 with Fe2O3/FeOOH cement)
sedimentary
Brecciated Chert
Sedimentary Chert (SiO2) with Calc-Silicate mineralization
sedimentary
Diorite (or salt-and-pepper granite pebble)
Phaneritic Igneous Rock (Intermediate Composition)
igneous
Basalt River Pebble
Basalt
igneous
Mixed river pebbles and quartz-rich specimens
Polymictic fluvial gravel; likely quartz, quartzite, chert, and weathered feldspathic rocks
sedimentary
Quartzite River Stone
Quartzite (primarily SiO2)
metamorphic
Granite Gravel / Crushed Granite
Plutonic Felsic Igneous Rock
igneous
Granite
Granite (Felsic Plutonic Rock)
igneous
Granite Cobble
Plutonic Igneous Rock (Granitic)
igneous
Mica Schist
Foliated Metamorphic Rock (Schist)
metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with mica or feldspar
metamorphic
Quartz-rich hydrothermal ore rock, likely gold-bearing quartz vein
Milky quartz (SiO₂) with iron-oxide staining and probable sulfide minerals; host rock may be schist or altered granite
metamorphic
Quartz (Chert/Chalcedony variety)
Silicon Dioxide (SiO2)
mineral
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly crystalline quartz (SiO₂), possibly with mica and feldspar
metamorphic
Petrified Wood
Silicified Wood (SiO2)
fossil
Granite-like rock
Felsic intrusive igneous rock, likely granite or granodiorite
igneous
Unidentified gray stone
Likely quartz-rich stone; exact identification is not possible from the image
mineral
Chert (Flint) / Silicified Limestone
Microcrystalline Quartz (SiO2)
sedimentary
Quartzite
Quartzite (SiO2)
metamorphic
Petrified Wood
Silicified Wood (SiO2)
mineral
Chert (Jasper)
Silicon Dioxide (SiO2)
sedimentary
Peridotite (with Olivine and Pyroxene)
Ultramafic Magmatic Rock (Primary minerals: (Mg, Fe)2SiO4 and (Ca, Mg, Fe)2Si2O6)
igneous
Quartzite River Rock
Quartzite
metamorphic
Beach Quartzite Pebble
Quartzite (primarily SiO2)
metamorphic
Dalmatian jasper
Orbicular microcrystalline quartz rock, commonly rhyolitic or volcanic-feldspar matrix with black arfvedsonite/alkali-amphibole inclusions
igneous
Diorite
Intermediate Phaneritic Plutonic Rock - Diorite
igneous