Sandstone (Quartzose)
Arenite (primarily SiO2)
sedimentary
Category
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Porphyritic Basalt (River Rock)
Porphyritic Basalt
igneous
Granite Pebble
Intrusive Igneous Rock
igneous
Glacial Cobble with Granite Inclusion
Porphyritic Basalt or Andesite containing Granitic Xenolith
igneous
Likely quartz-rich rock fragment
Indeterminate; possibly quartz-bearing granite or quartzite
igneous
Weathered quartz-rich pebble, possibly granite or pegmatite
Quartz (SiO₂) with probable feldspar and minor mica/iron-oxide inclusions
igneous
Peridotite
Ultramafic intrusive igneous rock
igneous
Quartz Pebble (with Iron Staining)
Crystalline Silicon Dioxide (SiO2)
mineral
Schist
Schist (metamorphic rock)
metamorphic
Pahoehoe Basalt
Extrusive mafic volcanic rock
igneous
Unakite
Epidotized Granite
metamorphic
Vesicular Basalt (Scoria)
Vesicular Basalt
igneous
Manhattan Schist
Manhattan Schist (Aluminous Metasedimentary Rock)
metamorphic
Decorative polished pebbles
Likely mixed quartz-rich lithologies, including quartzite, jasper, and/or basalt
mineral
Quartz-veined Sandstone Pebble
Quartzite-veined Arenite
sedimentary
Sandstone (with Iron Staining)
Clastic Sedimentary Rock (primarily Quartz with Limonite/Goethite staining)
sedimentary
Unakite
Epidotized Granite
metamorphic
Shale
Shale (Lutite)
sedimentary
Tiger Iron
Tiger Iron (Composition: SiO2, Fe2O3, Fe3O4)
metamorphic
Pink Quartzite
Quartzite (SiO2 with minor iron oxide impurities)
metamorphic
Shale
Fissile mudrock (composed primarily of clay minerals and quartz)
sedimentary
Vesicular Basalt (or Scoria)
Vesicular Basalt (Aphanitic-vesicular volcanic rock)
igneous
Layered sandstone
Quartz-rich sandstone, likely arkosic or lithic sandstone
sedimentary
Weathered granitic rock
Granite, likely quartz–feldspar–mica aggregate
igneous
Unknown Rock
Unknown
rock
Basalt with Calcite Veins
Basalt (containing CaCO3 inclusions)
igneous
Quartz Pebble (Geode Fragment / Druzy Cavity)
Silicon Dioxide (SiO2)
mineral
Rounded gray pebble, likely quartz-rich stone
Indeterminate; possibly quartzite or a weathered granitic pebble
rock
Quartz in Matrix (possibly Basalt or Siltstone host)
Silicon Dioxide (SiO2) in Host Rock
mineral
Mixed Rock Collection
Polylithic Geological Specimen Mix
sedimentary and igneous
Black Limestone with Calcite Veining
Bituminous Limestone (CaCO3 with Organic Carbon inclusions)
sedimentary
Weathered quartz-rich rock, possibly vein quartz
Quartz-rich rock; predominantly silicon dioxide (SiO₂), exact rock type uncertain from the photograph
metamorphic
Shale
Argillaceous sedimentary rock
sedimentary
Agate
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Quartz Veined Rock (Likely Graywacke or Quartzite)
Silicon Dioxide (SiO2) veins in Metasedimentary matrix
metamorphic
Sandstone or Quartzite pebble
Sandstone (Quartz arenite) or Quartzite
sedimentary or metamorphic
River Cobble (Basalt or Sandstone)
Weathered Basalt or Fine-Grained Sandstone
igneous
Mixed River Pebbles (including Unakite and Jasper)
Polymineralic geological specimens
igneous and sedimentary
Greenstone (likely chlorite-rich metamorphic rock)
Chlorite-bearing greenschist; exact identification requires testing
metamorphic
Hag Stone
Perforated sedimentary rock (typically flint, chert, or limestone)
sedimentary
Pumice
Pumice (Vesicular Rhyolite/Andesite)
igneous
Quartz–iron-oxide breccia or weathered quartz-bearing rock
Quartz (SiO₂) with limonite/goethite and possibly iron sulfides in a brecciated host
mineral