Slate
Slate; predominantly fine-grained phyllosilicates (muscovite/illite, chlorite) with quartz and feldspar
metamorphic
Category
Igneous, Sedimentary, Or Metamorphic (Mineral Based)
Browse igneous, sedimentary, or metamorphic (mineral based) specimens identified by the Rock Identifier community.
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Breccia
Breccia
sedimentary
Likely biotite-bearing metamorphic rock (schist or gneiss)
Mica schist/gneiss; chiefly quartz, feldspar, and biotite mica
metamorphic
Granite Thin Section
Granitic rock (Phaneritic texture)
igneous
Blue Apatite
Fluorapatite (Ca5(PO4)3F)
mineral
Polished pink quartzite or jasper
Quartzite, predominantly SiO₂; possibly iron-stained jasper/chalcedony
metamorphic
Sandstone
Arenite (SiO2 based typically)
sedimentary
Amethyst
Silicon Dioxide with iron impurities (SiO2)
mineral
Milky Quartz with Chlorite/Mica inclusions
Silicon Dioxide (SiO2) with inclusions
mineral
Sandstone
Arenite (SiO2 based with cement)
sedimentary
Mixed Tumbled Gemstones (Agate, Aventurine, Pyrite, etc.)
Multiple (principally Silicon Dioxide SiO2 and Iron Disulfide FeS2)
mineral
Muscovite Mica
Muscovite (KAl2(AlSi3O10)(OH)2)
mineral
Milky quartz-bearing rock, possibly quartzite
Quartz (SiO₂), likely in a quartzite or quartz-rich metamorphic matrix
metamorphic
Gneiss
Foliated Metamorphic Rock (Gneiss)
metamorphic
Weathered quartz-rich pebble
Likely quartz-bearing granite or granitic gneiss; exact identification requires testing
igneous
Red Sandstone
Arenite (SiO2 based with Fe2O3)
sedimentary
Sandstone
Arenite
sedimentary
Anthracite Coal
Anthracite (Carbon-based sedimentary rock typically classified as metamorphic)
metamorphic
Unakite
Altered Granite (Epidotized Granite)
metamorphic
Green Aventurine
Quartzite with Fuchsite inclusions (SiO2 + K(Al,Cr)2AlSi3O10(OH)2)
metamorphic
Blue Apatite
Apatite (Ca5(PO4)3(F,Cl,OH))
mineral
Banded Gneiss
Gneiss (High-grade Metamorphic Rock)
metamorphic
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Apatite
Ca5(PO4)3(F,Cl,OH)
mineral
Quartzite pebble
Quartzite (SiO2 based)
metamorphic
Muscovite
Muscovite, KAl2(AlSi3O10)(OH)2
mineral
Apatite
Calcium phosphate fluoride/chloride, Ca5(PO4)3(F,Cl,OH)
mineral
Weathered greenish-brown rock, likely serpentinized ultramafic rock
Serpentinite; chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), possibly with olivine, pyroxene, magnetite, or carbonate
metamorphic
River Pebble
Quartzite / Weathered Sedimentary Rock
sedimentary
Tumbled yellow jasper or chert
Microcrystalline quartz (SiO₂), likely iron-oxide-stained chalcedony/chert
mineral
Fossilized Shark Tooth
Bioapatite (Calcium Hydroxyapatite) replacement
mineral
Garnet (likely Almandine, Pyrope, or a blend)
Garnet group minerals: X3Y2(SiO4)3, where X and Y represent various metal ions (e.g., Almandine: Fe3Al2(SiO4)3, Pyrope: Mg3Al2(SiO4)3)
Mineral
Quartz pebble
Silicon dioxide (SiO2)
mineral
Dark gray rock fragment, likely basalt
Basalt; chiefly plagioclase feldspar and pyroxene, commonly with minor olivine and magnetite
igneous
Chert with Chalcedony/Quartz Vug
Cryptocrystalline Silica (SiO2)
sedimentary
Fluorite
Fluorite (Calcium Fluoride, CaF2)
mineral
Apatite
Calcium phosphate fluoride/chloride, Ca5(PO4)3(F,Cl,OH)
mineral
Biotite-rich gneiss or schist
Mica gneiss/schist; primarily quartz, feldspar, biotite, and possibly amphibole
metamorphic
Rose Quartz
Silicon Dioxide (SiO2) with trace Titanium, Manganese, or Iron
mineral
Biotite Schist
Biotite-rich Schist (K(Mg,Fe)3AlSi3O10(OH,F)2)
metamorphic
Biotite (Black Mica)
Biotite - K(Mg,Fe)3(AlSi3O10)(F,OH)2
mineral
Sandstone
Arenite (SiO2 based typically)
sedimentary