Basalt
Basalt (Aphanitic Mafic Volcanic Rock)
igneous
Category
Not A Rock (Synthetic Material)
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Limestone
Calcium Carbonate (CaCO3)
sedimentary
Polished dendritic jasper or agate slab
Microcrystalline quartz (SiO₂), likely jasper with chalcedony and iron/manganese dendrites
mineral
Tumbled blue quartzite or blue chalcedony (uncertain)
Quartz-rich rock; predominantly silicon dioxide (SiO₂)
metamorphic
Petrified Wood
Silicified Wood (primarily SiO₂ / Silicon Dioxide)
mineral
Pyrite (on host rock)
Iron Sulfide (FeS2)
mineral
Rounded pink granite pebble
Granite, chiefly quartz, alkali feldspar, plagioclase, and minor biotite/hornblende
igneous
Sandstone (Quartzose)
Arenite (primarily SiO2)
sedimentary
Sandstone
Arenite (composed primarily of SiO2)
sedimentary
Petrified Wood
Silicon Dioxide Fossilized Wood (SiO2)
fossil
Tumbled jasper or brecciated jasper
Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and dark mineral inclusions
mineral
Serpentinite
Serpentinite (composed largely of serpentine minerals like antigorite, lizardite, or chrysotile)
metamorphic
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Basalt with Caliche
Extrusive Mafic Igneous Rock with Secondary Carbonate Crust
igneous
Orange Quartzite (Tumbled Beach Pebble)
Quartzite (primarily SiO2)
metamorphic
Banded Chert (likely Flint or Jasper variety)
Silicon Dioxide (SiO2)
sedimentary
Chert
Chert (Microcrystalline Quartz, SiO2)
sedimentary
Chalcedony (Agate/Carnelian variant)
Silicon Dioxide (SiO2)
mineral
Moss agate bracelet
Chalcedony (microcrystalline quartz, SiO₂) with chlorite/amphibole inclusions
gemstone
Biotite Mica in Host Rock
Biotite (K(Mg,Fe)3AlSi3O10(F,OH)2)
mineral
Chert (with Quartz veins)
Microcrystalline Quartz (SiO2)
sedimentary
Fossilized Gastropod Internal Mold
Gastropoda (Steinkern fossil)
fossil
Polished carnelian/chalcedony pebble
Microcrystalline quartz (SiO₂), likely iron-stained chalcedony
gemstone
Weathered brown rock, likely iron-stained sandstone or chert
Indeterminate; probable quartz-rich sandstone/chert with iron-oxide staining
sedimentary
Leopard Skin Jasper
Orbicular Rhyolite (Silicon Dioxide with various impurities)
sedimentary
Red jasper (tumbled river pebble)
Jasper, an opaque microcrystalline variety of quartz/chalcedony (SiO₂), colored mainly by iron oxides
mineral
Diorite (Salt and Pepper Rock)
Phaneritic Plutonic Diorite (Plagioclase Feldspar + Amphibole/Biotite)
igneous
Granite Pebble
Granite (Plutonic Igneous Rock)
igneous
Yellow Jasper
Silicon Dioxide (SiO2) with Goethite/Iron oxide impurities
sedimentary (chemical)
Quartzite
Quartzite (SiO2)
metamorphic
Weathered granite-like rock
Coarse-grained granitic rock, likely quartz–feldspar–mica aggregate
igneous
Limestone
Sedimentary Rock (Primarily Calcium Carbonate, CaCO3)
sedimentary
Porphyritic Basalt (Peanut Obsidian/Star Galaxy-style)
Porphyritic Basalt (Silica-rich Volcanic Rock)
igneous
Banded gneiss (weathered glacial erratic)
Gneiss; typically quartz–feldspar–biotite ± hornblende
metamorphic
Quartzite
Quartzite (primarily SiO2)
metamorphic
Tumbled gneiss
Gneiss, chiefly quartz–feldspar with mica and dark ferromagnesian minerals
metamorphic
Chert Pebble with Quartz Veins
Microcrystalline Quartz (SiO2)
sedimentary
Diorite
Intermediate Phaneritic Igneous Rock (Diorite)
igneous
Diorite
Phaneritic Intermediate Plutonic Rock (Diorite)
igneous
Ferruginous Conglomerate
Ferruginous Conglomerate (Clastic Sedimentary Rock)
sedimentary
Granite River Pebble
Phaneritic Felsic Igneous Rock (Granite)
igneous
Muscovite Mica
Muscovite - KAl2(AlSi3O10)(F,OH)2
mineral