Weathered brown stone, possibly basalt or iron-rich sedimentary rock
Indeterminate from photograph; likely fine-grained mafic rock (basalt) or ferruginous sandstone
igneous
Category
Synthetic (Not A Natural Rock)
Browse synthetic (not a natural rock) specimens identified by the Rock Identifier community.
Learn about Synthetic (Not A Natural Rock) in the encyclopedia
View all →
Granite
Phaneritic plutonic rock (dominated by SiO2, Al2O3, K2O, Na2O)
igneous
Red Coral
Corallium rubrum
gemstone
Polished dark stone, likely basalt
Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine
igneous
Sandstone
Arenite (composed primarily of Quartz: SiO2)
sedimentary
Green Aventurine
Quartzite with Fuchsite inclusions (SiO2 + K(Al,Cr)2(AlSi3O10)(OH)2)
metamorphic
Granite
Phaneritic Igneous Rock (primarily Quartz, Feldspar, and Mica)
igneous
Dyed or color-enhanced agate/microcrystalline quartz bead
Chalcedony (microcrystalline SiO₂), likely agate
gemstone
Black Onyx
Chalcedony (Silicon Dioxide, SiO2)
mineral
Shale creek bed
Shale (fine-grained clastic sedimentary rock)
Sedimentary
Green Druzy Quartz (Prasiolite)
Silicon Dioxide (SiO2) with inclusions (typically Chlorite or Actinolite)
mineral
Banded Agate (Onyx type)
Silicon Dioxide (SiO2) - Cryptocrystalline Quartz
mineral
Quartz Druze (on Matrix)
Silicon Dioxide (SiO2)
mineral
Tumbled turquoise
Turquoise — hydrated copper aluminum phosphate, CuAl₆(PO₄)₄(OH)₈·4H₂O
mineral
Polished pink chalcedony (likely pink agate/geode)
Microcrystalline quartz, SiO₂; chalcedony with iron-bearing inclusions and possible druzy quartz
mineral
Sapphire
Corundum (Al₂O₃) with trace elements causing color variations.
Mineral
Precious Coral
Corallium rubrum (Calcium carbonate with trace carotene)
Organic gemstone / Sedimentary mineraloid
Greenstone / serpentinized ultramafic rock (probable)
Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with possible magnetite and talc
metamorphic
Black Onyx
Silicon dioxide (SiO2) - Chalcedony variety
mineral
Turquoise
CuAl6(PO4)4(OH)8·4H2O
mineral
Weathered gray stone, possibly limestone or concrete-like carbonate rock
Tentatively micritic limestone (calcium carbonate, CaCO₃); exact identification is uncertain from the image
sedimentary
Smoky Quartz
Smoky Quartz (SiO ₂)
Mineral
Quartzite
Quartzite (primarily SiO2)
Metamorphic
Asphalt (Bituminous Concrete)
Asphaltum / Bitumen-Aggregate Matrix
Technonatural composite (often containing sedimentary/igneous aggregate)
Rounded weathered pebble, likely sandstone or altered limestone
Indeterminate clastic carbonate/siliciclastic rock; exact identification requires a fresh surface and tests
sedimentary
Limonite / Goethite Ironstone
FeO(OH)·nH2O (Hydrous iron oxide)
mineral
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Amethyst
SiO2 (Silicon Dioxide with Iron impurities and natural radiation influence)
mineral
Obsidian
Volcanic glass (silica-rich rhyolitic melt; primarily SiO₂)
igneous
Druzy Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Granite
Granite (Phaneritic intrusive igneous rock) - Composition: SiO2, Al2O3, K2O, Na2O
igneous
Quartzite
Quartzite
Metamorphic
Granite
Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Mica)
igneous
Shale
Shale (clastic sedimentary rock)
Sedimentary
Granite
Granite (phaneritic intrusive igneous rock consisting mainly of quartz, alkali feldspar, and plagioclase)
igneous
Quartz (various varieties)
SiO₂ (Silicon Dioxide)
Mineral
Sandstone
Arenite (general term for sandstone)
Sedimentary Rock
Ammonite Fossil
Ammonoidea
fossil
Possible tektite or dark volcanic rock fragment
Uncertain; likely natural silicate glass (tektite) or basalt
mineral
Small rounded pebble
Indeterminate lithic grain; likely weathered sandstone, iron-stained quartz-rich rock, or a concretion
sedimentary
Moldavite
SiO2 (+ Al2O3, FeO, K2O) - Natural Tektite Glass
gemstone
Quartz (likely) or a Quartzite Pebble
Silicon dioxide (SiO2) for quartz. If it's quartzite, it's a metamorphic rock primarily composed of quartz.
Mineral, specifically a detrital grain