Porphyritic Basalt (or Andesite) Pebble
Porphyritic Mafic Volcanic Rock
igneous
Category
Not A Rock (Synthetic Material)
Browse not a rock (synthetic material) specimens identified by the Rock Identifier community.
Learn about Not A Rock (Synthetic Material) in the encyclopedia
View all →
Basalt
Basalt (Mafic volcanic rock)
igneous
Dacite
Dacite (intermediate volcanic rock)
igneous
Granite Cobble
Phaneritic Felsic Igneous Rock
igneous
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Quartzite
Quartzite (predominantly SiO2)
metamorphic
Limestone ( weathered ) / Chert Nodular Rock
Sedimentary rock (primarily Calcium Carbonate, CaCO3, with Microcrystalline Quartz, SiO2)
sedimentary
Chevron Amethyst
Silicon Dioxide (SiO2) with iron impurities
mineral
Small tumbled dark stone, possibly basalt or slag
Likely fine-grained basalt; exact identification is uncertain from the photograph
igneous
Quartzite (River Pebble)
Metamorphosed Quartz Sandstone (SiO2)
metamorphic
Limestone Boulder
Sedimentary Rock (Calcium Carbonate, CaCO3)
sedimentary
Pink Granite
Granite (Felsic Plutonic Igneous Rock)
igneous
Sandstone (Ferruginous)
Clastic sedimentary rock (SiO2 with Fe2O3)
sedimentary
Sandstone (with Iron Staining)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Sandstone (Ferruginous)
Clastic Sedimentary Rock (SiO2 with Fe2O3)
sedimentary
Turquoise in Matrix
CuAl6(PO4)4(OH)8·4H2O
gemstone
Chert (Flint / Jasper)
Silicon Dioxide (SiO2)
sedimentary
Precious Opal in Matrix
Hydrated Silica (SiO2·nH2O)
mineral
Weathered granitic rock
Granite or granodiorite, likely quartz–feldspar–mica aggregate
igneous
Quartzite
Quartzite (SiO2)
metamorphic
Sandstone (Pebble)
Arenite (primarily SiO2)
sedimentary
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly crystalline SiO₂, possibly with iron-oxide staining and minor feldspar or mica
metamorphic
Gneiss
Gneiss (a rock type, not a specific mineral with a formula)
Metamorphic Rock
Diamond (as set in a metal alloy ring)
Diamond (Pure Carbon, C)
mineral
Sandstone (Quartzose / Feldspathic Sandstone)
Arenite (SiO2 principal matrix)
sedimentary
Serpentine
Antigorite/Chrysotile group (Mg3Si2O5(OH)4)
metamorphic
Vesicular basalt (likely weathered scoria)
Basaltic volcanic rock; chiefly plagioclase, clinopyroxene, and olivine with vesicles
igneous
Chert Nodule
Microcrystalline Silica (SiO2)
sedimentary
Blue Lace Agate (with Amethyst Geode center)
Silicon Dioxide (SiO2) - Cryptocrystalline Chalcedony
mineral
Fossilized Shark Tooth
Chondrichthyes (Class)
fossil
Granite
Granite (Phaneritic intrusive igneous rock)
igneous
Tumbled pegmatitic granite
Coarse-grained granite/pegmatite, chiefly quartz, feldspar, and biotite or amphibole
igneous
Quartz geode (likely amethyst-bearing)
Silica geode; quartz, SiO₂, with possible amethyst and minor iron oxides
mineral
Water-worn basalt cobble
Basalt; chiefly plagioclase feldspar, pyroxene, and minor olivine/iron oxides
igneous
Red Sandstone
Sandstone (Iron Oxide Rich)
sedimentary
Red Sandstone
Arenite (with Iron Oxide / Hematite cementation)
sedimentary
Quartz Geode
Silicon Dioxide (SiO2) within a geode
sedimentary
Quartzite
Quartzite (SiO2)
metamorphic
Possible iron-rich basalt or industrial slag
Basalt, likely Fe–Mg silicate rock; exact identification is uncertain from the blurred image
igneous
Quartzite Pebble
Metaquartzite
metamorphic
Red Sandstone
Arenite (high iron oxide content)
sedimentary