Marble
Crystalline Limestone (mostly CaCO3 / Calcium Carbonate)
Category
Browse sedimentary or metamorphic (low grade) specimens identified by the Rock Identifier community.
Marble
Crystalline Limestone (mostly CaCO3 / Calcium Carbonate)
Jasper
Silicon dioxide (SiO2) with impurities
Amphibolite
Amphibolite (rich in amphibole and plagioclase feldspar)
Carnelian (Chalcedony)
SiO2 (Silicon Dioxide - Microcrystalline Quartz)
Pyrite
Iron Sulfide (FeS2)
Goethite / Limonite Concretion
Iron Hydroxide Oxide (FeO(OH))
Pyrite (Fool's Gold)
Iron Sulfide (FeS2)
Gneiss
Gneiss (High-grade metamorphic rock)
Ironstone Nodule
Ferruginous Sandstone / Limonite Concretion
Chalcedony (Moonstone variant or White Agate)
Silicon Dioxide (SiO₂)
Emerald in Matrix
Beryl (Be3Al2(SiO3)6) with Chromium/Vanadium impurities
Blue Sapphire
Corundum (Al2O3)
Glauconite sand
Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2
Limonite (Iron Ore)
Hydrated iron(III) oxide-hydroxide (FeO(OH)·nH2O)
Citrine Quartz Crystal Cluster
Silicon Dioxide (SiO2) with iron impurities
Carnelian Agate
Chalcedony (Silicon Dioxide, SiO2) with Iron Oxide impurities
Carnelian (Tumbled)
Silicon Dioxide (SiO2)
Carnelian
Carnelian (SiO2 with iron oxide impurities)
Limonite (Iron Ore)
FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide)
Blue Chalcedony
Cryptocrystalline Quartz (SiO2)
Pyrite
Iron Sulfide (FeS2)
Ferruginous Sandstone (Gritstone)
Clastic sedimentary rock with iron-rich cement (FeO(OH)·nH2O)
Blue Chalcedony
Cryptocrystalline Quartz (SiO2)
Amethyst and Calcite collection
Silicon Dioxide (SiO2) and Calcium Carbonate (CaCO3)
Limonite (Ironstone)
Limonite (mixture of hydrated iron(III) oxide-hydroxides)
Anthracite Coal
Anthracite (Carbon Content 86–97%)
Conglomerate
Conglomerate (clastic sedimentary rock)
Serpentine (likely serpentinite)
Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), commonly with magnetite and chromite
Quartz (Iron-Stained or Milky Quartz)
Silicon Dioxide (SiO2)
Whetstone (Arkansas Stone)
Novaculite (SiO2)
Common Opal
SiO2·nH2O (Hydrated Silicon Dioxide)
Pyrite
Iron Sulfide (FeS2)
Pyrite
Iron Sulfide (FeS2)
Prehnite
Prehnite (Ca2Al(AlSi3O10)(OH)2)
Tiger's Eye
SiO2 (Quartz with inclusion of iron oxides)
Anthracite Coal
Anthracite (Carbon-based metamorphic rock, 86-97% C)
Conglomerate
Clastic Sedimentary Rock (Puddingstone)
Staurolite-bearing mica schist (probable)
Mica schist composed chiefly of muscovite/biotite, quartz, and likely staurolite or garnet
Schist
Mica Schist
Quartz-bearing granite or granitic pegmatite
Felsic intrusive rock, chiefly quartz (SiO₂), feldspar, and minor mica
Limonite Nodules / Goethite
Hydrated Iron Oxide-Hydroxide (FeO(OH)·nH2O / Fe2O3·nH2O)
Serpentinized ultramafic rock (serpentinite)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with possible magnetite, chromite, talc, and carbonate