Agate (specifically a Yellow/Honey Agate)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
mineral
Category
Rock
Browse rock specimens identified by the Rock Identifier community.
Quartz Crystal on Matrix
Silicon Dioxide (SiO2)
mineral
Serpentine (likely greenstone)
Serpentine-group minerals, chiefly antigorite, lizardite, and chrysotile; commonly with magnesite or magnetite
metamorphic
Shale
Fissile mudrock (composed of clay-sized particles and detrital grains)
sedimentary
Limestone
Sedimentary Calcium Carbonate (CaCO3)
sedimentary
Banded Gneiss
Gneiss (Metamorphic Rock)
metamorphic
Sandstone
Sandstone (composed predominantly of Quartz, SiO2)
sedimentary
Red Scoria
Scoria (Vesicular Basalt/Andesite)
igneous
Quartz Vein in Gneiss or Basalt
Milky Quartz (SiO2) within Metamorphic Host Rock
Metamorphic or Igneous with Mineral Inclusion
Pebble (Likely Basalt or Siltstone)
Clastic sedimentary rock or mafic volcanic rock
Igneous or Sedimentary
Basalt with Quartz/Calcite Veins
Basalt with hydrothermal vein infill
igneous
Quartz (Druzy)
Silicon Dioxide (SiO2)
mineral
Quartz vein in dark host rock
Quartz (SiO₂), likely in basalt, gabbro, or altered mafic rock
mineral
Milky Quartz
Quartz (Silica / Silicon Dioxide), SiO2
mineral
Fossiliferous Limestone (Coquina)
Biogenic Limestone (Calcium Carbonate, CaCO3)
sedimentary
Shale
Shale (claystone/mudstone)
sedimentary
Gneiss, likely migmatitic or granitic gneiss
Banded quartz–feldspar–mica gneiss; composition chiefly quartz, alkali/plagioclase feldspar, biotite and accessory minerals
metamorphic
Polished banded gneiss
Biotite–quartz–feldspar gneiss, locally migmatitic
metamorphic
Weathered granite fragment
Granite, primarily quartz, feldspar, and mica
igneous
Quartz Vein in Basalt or Slate
Hydrothermal quartz vein traversing mafic host rock
metamorphic
Rhyolite with Lithophysae and Iron Oxide
Extrusive igneous rock / Felsic volcanic rock
igneous
River Stone (Basalt or Siltstone)
Mafic Volcanic Rock or Clastic Sedimentary Rock
igneous or sedimentary
Basalt
Basalt (Aphanitic Mafic Igneous Rock)
igneous
Sandstone (with Iron Staining)
Clastic sedimentary rock (SiO2 with Fe2O3 oxides)
sedimentary
Mixed Rock and Mineral Collection
Various geological specimens
igneous, sedimentary, and metamorphic
Coquina / Fossiliferous Limestone
Fossiliferous Limestone (CaCO3)
Sedimentary
Granite
Intrusive Igneous Rock
igneous
Druzy Quartz on Sandstone
Silicon Dioxide (SiO2) with Quartz Crystals on Clastic Sedimentary Rock
sedimentary
Gneiss
Gneiss (High-grade metamorphic rock)
metamorphic
Weathered granitic or gneissic cobble
Likely altered granite/granodiorite; exact identification requires a fresh surface and testing
igneous
Quartz-Veined Gneiss or Metamorphic Rock with Quartz Veins
Quartz-veined metamorphic rock (Silicate mineral assemblage)
metamorphic
Eroded Brick or Pumice-like Scoria
Vesicular Basalt / Scoria (Anthropogenic variant: Eroded Firebrick)
igneous
Granite Pebble
Intrusive Igneous Rock
igneous
Red jasper
Jasper, an opaque microcrystalline quartz variety (SiO₂), colored mainly by iron oxides
mineral
Shale
Laminated Fissile Pelite
sedimentary
Dalmatian Stone
Peralkaline Quartz-Feldspar Porphyry with Arfvedsonite
igneous
Serpentine-rich greenstone
Serpentinite, dominated by serpentine-group minerals (antigorite/lizardite/chrysotile), with possible chlorite, magnetite, and talc
metamorphic
Granite fragment
Granite, chiefly quartz (SiO₂), feldspar, and mica
igneous
Rounded gray pebble, likely basalt or andesite
Fine-grained mafic to intermediate volcanic rock; commonly basalt (plagioclase ± pyroxene/olivine)
igneous
Brecciated Jasper
Silicon Dioxide (SiO2) with iron oxide inclusions
sedimentary
Granodiorite with Quartz Veining
Granodiorite (containing Plagioclase Feldspar, Quartz, and Biotite/Hornblende) with Quartz (SiO2) veins
igneous
Basalt
Basalt
igneous