Limonite Concretion
Limonite (Hydrated iron(III) oxide-hydroxides, FeO(OH)·nH2O)
sedimentary
Category
Sedimentary Rock (Possibly Composed Of Various Minerals)
Browse sedimentary rock (possibly composed of various minerals) specimens identified by the Rock Identifier community.
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Clear quartz (rock crystal), possibly a small rough fragment
Quartz, silicon dioxide (SiO₂)
mineral
Dark gray fine-grained rock, possibly basalt
Basalt; primarily plagioclase feldspar and pyroxene, with possible olivine or magnetite
igneous
River Siltstone / Mudstone Pebble
Siltstone (composed of mixed silicate and carbonate minerals)
sedimentary
Quartz
Silicon Dioxide (SiO2)
mineral
Sandstone
Clastic Sedimentary Rock
sedimentary
Sandstone (Ferruginous)
Clastic sedimentary rock (primarily SiO2 with Fe2O3 cement)
sedimentary
Sandstone
Clastic sedimentary rock (Quartz arenite)
sedimentary
Sandstone
Clastic Sedimentary Rock
sedimentary
Limonite / Iron Concretion
Limonite (FeO(OH)·nH2O)
mineral
Quartzite
Quartzite (composed primarily of SiO2)
metamorphic
Banded gneiss
Gneiss, commonly quartz–feldspar–mica gneiss
metamorphic
Ammonite Fossil
Subclass Ammonoidea
fossil
Sandstone
Sedimentary Clastic Rock
sedimentary
Iron-rich rock, possibly ironstone
Likely ferruginous sandstone or ironstone; exact identification requires testing
sedimentary
Granite
Granite
igneous
Greenschist
Greenschist (composed of Chlorite, Actinolite, and Epidote)
metamorphic
Iron-stained quartz vein rock
Quartz-rich vein material, predominantly SiO₂, with iron oxyhydroxides (goethite/limonite) and likely sulfide alteration
metamorphic
Quartz with Chalcedony
Silicon Dioxide (SiO2)
mineral
Limonite
FeO(OH)·nH2O
mineral
Chert (Flint)
Silicon dioxide (SiO2)
sedimentary
Likely mica schist with garnet
Garnet-bearing mica schist, probably containing biotite/muscovite and almandine garnet
metamorphic
Marble
Marbles are primarily composed of calcite (calcium carbonate, CaCO3) or dolomite (calcium magnesium carbonate, CaMg(CO3)2).
Metamorphic Rock
Sandstone
Sedimentary Rock (Quartz arenite)
sedimentary
Quartz-rich rock or quartz specimen
Quartz (SiO₂), likely massive quartz or quartz-bearing host rock
mineral
Chalcedony
Silicon dioxide (SiO2)
mineral
Sandstone
Clastic sedimentary rock
sedimentary
Sandstone
Clastic Sedimentary Rock
sedimentary
Sandstone
Clastic Sedimentary Rock
sedimentary
Sandstone
Sedimentary Rock (Quartz arenite/Arkose)
sedimentary
Polished banded gneiss or schist pebble
Banded quartz–feldspar–mica gneiss (tentative)
metamorphic
Sandstone
Arenite (Siliclastic Sedimentary Rock)
sedimentary
Small weathered rock fragment
Indeterminate; possibly limestone or altered volcanic rock
sedimentary
Limonite
FeO(OH)•nH2O
mineral
Limonite
FeO(OH)•nH2O
mineral
Sandstone
Clastic Sedimentary Rock
sedimentary
Tumbled quartz-rich pebble
Microcrystalline quartz (SiO₂), possibly milky quartz or chalcedony
mineral
Sandstone (Banded)
Sedimentary Clastic Rock
sedimentary
Quartz
Silicon Dioxide (SiO2)
mineral
Unidentified dark mineral/rock fragment
Indeterminate; appearance may fit a sulfide-bearing rock or iron-rich mineral
mineral
Small brown rock fragment, possibly iron-stained quartz or chert
Unidentifiable from the photograph; potentially quartz (SiO₂) or microcrystalline silica (chalcedony/chert)
mineral
Likely graphite-rich schist
Graphite-bearing schist, composed mainly of graphite with possible mica and quartz
metamorphic