Sandstone
Clastic sedimentary rock (primarily SiO2)
sedimentary
Category
Not A Rock
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Granite River Rock
Intrusive igneous rock (composed mainly of quartz, alkali feldspar, and plagioclase)
igneous
Painted River Pebble (likely Basalt or Greywacke)
Aphanitic Lithic Clast with Anthropogenic Pigment coating
Sedimentary or Igneous
Weathered granite or granitic gneiss pebble
Granite; primarily quartz, potassium feldspar, plagioclase, and mica
igneous
Likely gneiss
Gneiss, composed chiefly of quartz, feldspar, and mica/amphibole
metamorphic
Amber-bearing Coal/Sedimentary Rock
Bituminous coal or carbonaceous siltstone with Fossilized Tree Resin (C10H16O)
sedimentary
Jasper and Quartz Breccia
Silicified Breccia (Quartz / Chalcedony / Hematite)
sedimentary
Quartzite (Yellow/Orange variety)
Quartzite (primarily SiO2)
metamorphic
Tumbled serpentine with dark magnetite/chromite matrix
Serpentinite; chiefly antigorite/lizardite, Mg3Si2O5(OH)4, with magnetite and possibly chromite
metamorphic
Shale / Mudstone
Laminated Mudrock (Siliciclastic Sedimentary Rock)
sedimentary
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4
metamorphic
Agate Geode
Silicon Dioxide (SiO2) - Chalcedony variety
sedimentary
Vesicular Basalt (or Scoria)
Vesicular Basalt
igneous
Basalt
Basalt
igneous
Gneiss
High-grade regional metamorphic rock (Foliated)
metamorphic
Granite
Granite (Phaneritic intrusive igneous rock)
igneous
Basalt
Basalt
igneous
Shale (Beach-worn)
Laminated Pelite (primarily clay minerals and quartz)
sedimentary
Weathered granite or granitic gneiss
Granite: quartz, feldspar, and mica; possibly gneiss if the dark minerals are banded
igneous
Granite
Granite; primarily quartz (SiO₂), feldspar, and mica
igneous
Quartz-Veined Slate or Greenstone
Metamorphic rock with quartz vein (SiO2)
metamorphic
Basalt
Mafic extrusive igneous rock
igneous
Clear Quartz (Cut/Faceted Gemstone)
Silicon Dioxide (SiO2)
gemstone
Quartz Geode
Silicon Dioxide (SiO2)
mineral
Basalt with Alteration Crust
Basalt (SiO2 range 45-52%)
igneous
Leopard Skin Jasper
Orbicular Jasper (Silicon Dioxide, SiO2)
sedimentary
Basalt
Mafic Igneous Rock (composed primarily of plagioclase feldspar and pyroxene)
Igneous
Basalt
Basalt (Mafic volcanic rock)
igneous
Basalt Cobble
Aphanitic Mafic Igneous Rock (Basalt)
igneous
Basalt River Cobble
Basalt (Mafic volcanic rock)
igneous
Milky Quartz with Chlorite Schist Inclusions
Quartz (SiO2) with Chlorite Group silicates (typically (Mg,Fe)3(Si,Al)4O10(OH)2)
metamorphic
Granite
Phaneritic Igneous Rock (primarily Quartz, Feldspar, Mica)
igneous
Basalt with Weathering Rind
Basalt (Mafic Volcanic Rock)
igneous
River Rock / Stream Pebble
Fluvial Clast / Rounded Sedimentary Particle
Sedimentary Rock (possibly composed of various minerals)
Quartz Druzy (Geode Fragment)
Silicon Dioxide (SiO2)
mineral
Petrified Wood
Silicified wood (primarily quartz, SiO2)
fossil
Fossilized Bark
Lepidodendron / Sigillaria fossil impression
fossil
River Pebble (likely Quartzite or Siltstone)
Sedimentary Clast (SiO2 based)
sedimentary
Unknown Tumbled Stone
Unknown (Too Blurry)
mineral
Desert Rose (Gypsum Rose)
Calcium Sulfate Dihydrate (CaSO4·2H2O)
mineral
Porphyritic Basalt or Porphyritic Andesite
Porphyritic Extrusive Igneous Rock
igneous
Quartz Geode (likely within Limestone or Dolomite matrix)
Quartz (SiO₂)
Mineral within a Sedimentary Rock