Chert (Nodule)
Microcrystalline Quartz (SiO2)
sedimentary
Category
Not A Rock (Synthetic Material)
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Green Opal (Prase Opal)
SiO2 · nH2O (Hydrated Silicon Dioxide)
mineral
Mica-rich metamorphic rock, likely schist
Muscovite–biotite schist, possibly with quartz and feldspar
metamorphic
Petrified Wood
Silicified wood (primarily Silicon Dioxide, SiO2)
metamorphic
Petrified Wood
Silicified Wood (SiO2)
metamorphic
Unakite
Epidotized Granite
metamorphic
Black Marble
Recrystallized Carbonate Rock (CaCO3)
metamorphic
Likely quartz-rich metamorphic rock (quartzite or quartz-veined schist)
Quartzite/siliceous schist; chiefly quartz (SiO₂), with probable mica and iron-oxide staining
metamorphic
Faceted Glass (Costume Jewelry)
Amorphous Silicon Dioxide with colorants (Glass)
Synthetic/Man-made Material
Chalcedony in Matrix (likely Agatized Coral or Chert)
Silicon Dioxide (SiO2)
sedimentary
Quartzite
Metamorphic Quartz Arenite
metamorphic
Devil's Toenail
Gryphaea (extinct genus of foam oysters, typically composed of Calcite CaCO3)
sedimentary
Basalt with Quartz/Feldspar Inclusions
Amygdaloidal or Porphyritic Mafic Volcanic Rock with Siliceous Veining
igneous
Nuummite
Nuummite (Ortho-amphibole rock, primarily Anthophyllite and Gedrite)
metamorphic
Chert (Jasper/Flint variant)
Microcrystalline quartz (SiO2)
sedimentary
Coarse-grained granite or granitic pegmatite
Granite; primarily quartz (SiO₂), feldspar, and mica/amphibole
igneous
Weathered agate or chalcedony nodule
Microcrystalline quartz (SiO₂), likely agate/chalcedony with iron-oxide staining
mineral
Pink granite pebble
Granite, composed mainly of quartz, potassium feldspar, plagioclase feldspar, and biotite/hornblende
igneous
Sandstone (Quartz Arenite)
Sandstone (SiO2 with possible mineral cements)
sedimentary
Muscovite Mica
Muscovite / KAl2(AlSi3O10)(OH)2
mineral
Quartz (Rose or Milky)
Silicon Dioxide (SiO2)
mineral
Granite Boulder
Felsic Intrusive Igneous Rock
igneous
Sandstone
Arenite (SiO2 based clastic rock)
sedimentary
Conglomerate
Sedimentary Conglomerate
sedimentary
Chert Nodule (Flint)
Microcrystalline Quartz (SiO2)
sedimentary
Limestone with fossiliferous textures
Bioclastic Limestone (CaCO3)
sedimentary
Mica Schist
Mica Schist (primarily composed of Muscovite, Biotite, and Quartz)
metamorphic
Red Scoria (Lava Rock)
Vesicular Basalt / Scoria
igneous
Granodiorite
Granodiorite
igneous
Red Sandstone Pebble
Arenite with iron oxide (Hematite)
sedimentary
Sandstone (with Limonite staining)
Arenite (primarily SiO2 with FeO(OH)·nH2O)
sedimentary
Red Sandstone
Clastic sedimentary rock (Quartz arenite/Arkose)
sedimentary
Quartzite Pebble
Metamorphic rock primarily composed of Quartz (SiO2)
metamorphic
Gravel/Common Siltstone
Siltstone (fine-grained siliciclastic sedimentary rock)
sedimentary
Granite
Phaneritic plutonic rock (dominated by Quartz and Feldspar)
igneous
Granite
Granite (phaneritic felsic intrusive rock)
igneous
Chert
Microcrystalline Quartz (SiO2)
sedimentary
Sandstone
Arenite (SiO2 primarily)
sedimentary
Quartzite River Rock
Metamorphic Quartzite (SiO2)
metamorphic
Blue Apatite
Calcium phosphate mineral, Ca5(PO4)3(F,Cl,OH)
mineral
Moldavite
Moldavite (Silica-rich glass, SiO2 + Al2O3)
tektite
Quartz-rich metamorphic fragment (likely mica schist)
Mica schist, probably muscovite–quartz schist
metamorphic