Coal
Bituminous Coal / Anthracite
sedimentary
Category
Anthropogenic (Man Made Material Processed By Nature)
Browse anthropogenic (man made material processed by nature) specimens identified by the Rock Identifier community.
Learn about Anthropogenic (Man Made Material Processed By Nature) in the encyclopedia
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Milky Quartz
Silicon Dioxide (SiO2)
mineral
Shale with Plant Fossils / Carbonaceous Shale
Laminated Mudrock (Siliciclastic)
sedimentary
Chert
Chert (Microcrystalline Quartz)
sedimentary
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Chalcedony
Silicon Dioxide (SiO2)
mineral
Tumbled amethyst
Amethyst, purple quartz (SiO₂), colored by trace iron and irradiation
gemstone
Blue chalcedony (likely dyed or polished)
Chalcedony, microcrystalline quartz (SiO₂)
mineral
Weathered, porous limestone (probable fossiliferous limestone)
Calcite-rich limestone; predominantly CaCO₃
sedimentary
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Sandstone (Water-worn Cobble)
Arenite (SiO2 with CaCO3 or Fe2O3 cement)
sedimentary
Quartz (Milky Quartz)
Silicon Dioxide (SiO2)
mineral
Blue cabochon gemstone, likely sapphire
Corundum (Al₂O₃), blue variety colored mainly by iron and titanium
gemstone
Pearl
Calcium carbonate (CaCO3) - mainly Aragonite with Conchiolin
mineraloid
Cloudy Quartz
Silicon Dioxide (SiO2)
mineral
Sandstone
Arenite (mostly SiO2)
sedimentary
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Honey calcite (calcite-rich limestone/marble fragment)
Calcite — CaCO₃; likely coarse crystalline calcitic rock
mineral
Rock Specimen
Unclassified rock specimen
sedimentary
Faceted Gemstone
Unknown transparent mineral, possibly Diamond (C), Cubic Zirconia (ZrO2), Quartz (SiO2), or Glass
gemstone
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Seven Chakra Bonded Stone
Bonded composite of Red Jasper, Carnelian, Tiger's Eye, Aventurine, Lapis Lazuli, Amethyst, and Clear Quartz
metamorphic
Geode fragment, likely quartz-lined basalt or chalcedony nodule
Microcrystalline quartz (SiO₂), possibly with iron-oxide staining in a basaltic host
mineral
Pyrite in Quartz Matrix
Iron Sulfide (FeS2) embedded in Silicon Dioxide (SiO2)
mineral
Milky Quartz
Quartz (Silicon Dioxide - SiO2)
mineral
Granite
Phaneritic Felsic Igneous Rock (Granite)
igneous
Polished amber-colored stone, possibly chert or jasper
Uncertain from image; likely microcrystalline quartz (SiO₂) if chert/jasper
mineral
Heat-Treated Citrine
Silicon Dioxide (SiO2) with iron impurities
mineral
Granite Pebble
Granite; primarily composed of Quartz (SiO2), Feldspar (KAlSi3O8), and Mica
igneous
Tumbled and polished quartz crystal points
Quartz (silicon dioxide, SiO₂), chiefly rock crystal with smoky or included varieties
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Tumbled blue-gray stone beads, likely labradorite or dyed quartz
Probable labradorite (plagioclase feldspar; approximately NaAlSi₃O₈–CaAl₂Si₂O₈), though exact identification requires testing
mineral
Rounded gray-brown cobble, likely weathered sandstone or quartzite
Tentatively quartz-rich sandstone (SiO₂-dominated); exact identification requires hardness and acid tests
sedimentary
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Gypsum (Satin Spar / Alabaster variety)
Calcium Sulfate Dihydrate (CaSO4·2H2O)
mineral
Milky Quartz
Crystalline Quartz (SiO2)
mineral
Milky Quartz
Crystalline Silicon Dioxide (SiO2)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral