Amethyst
Amethyst (Silicon Dioxide with iron impurities, SiO2)
Category
Browse metamorphic or sedimentary depending on local grade specimens identified by the Rock Identifier community.
Amethyst
Amethyst (Silicon Dioxide with iron impurities, SiO2)
Chert (Iron-stained)
Microcrystalline silica (SiO2) with trace Iron oxide (Fe2O3)
Mica Schist (with Muscovite)
Muscovite/Quartz Schist (KAl2(AlSi3O10)(OH)2)
Orange Calcite
Calcite (Calcium Carbonate, CaCO3)
Smoky Quartz
Silicon Dioxide (SiO2)
Ruby
Corundum (Al2O3:Cr)
Pink Rhodonite
Manganese Silicate (MnSiO3)
Ferruginous Sandstone Pebble
Arenite with Iron-Oxide Cement (SiO2 with Fe2O3/FeO(OH) staining)
Banded Iron Formation (BIF)
Banded Iron Formation (composed primarily of Hematite [Fe2O3], Magnetite [Fe3O4], and Chert [SiO2])
Ventifact
Eolian Ventifact (often composed of basalt, chert, or quartzite)
Sandstone (specifically Arkose or Quartz Arenite)
Arenite (primarily SiO2 with possible Feldspar)
Graphite
Graphite (Carbon, C)
Graphite
Graphite (Native Carbon), Formula: C
Milky Quartz
Silicon Dioxide (SiO2)
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
Pyrite
Iron Disulfide (FeS2)
Moonstone
Adularia or Orthoclase (KAlSi3O8) or Albite (NaAlSi3O8), specifically with lamellar exsolution of albite and orthoclase.
Chert (or Flint)
Chert (microcrystalline or cryptocrystalline quartz, SiO2)
Pyrite
Iron Pyrite (FeS2)
Botryoidal Pyrite
Iron Sulfide (FeS2)
Jasper (Red Jasper)
Silicon Dioxide (SiO₂)
Citrine Quartz
Citrine (Silicon Dioxide, SiO2)
Sandstone Pebble (Quartzite-rich)
Clastic Terrigenous Sedimentary Rock (SiO2 dominant)
Chalcedony (Moonstone variant or White Agate)
Silicon Dioxide (SiO₂)
Ferruginous Sandstone (Ironstone)
Sedimentary rock with high iron oxide content (Fe2O3 / FeO(OH))
Carnelian (Red Chalcedony)
Silicon Dioxide (SiO2)
Limonite Concretion (Ironstone)
Limonite (FeO(OH)·nH2O) with Goethite and Hematite
Ironstone Concretion
Limonitic/Hematitic Concretion
Ironstone Concretion (Pot Stone)
Siderite or Limonite Concretion (FeCO3 or FeO(OH)·nH2O)
Chert (with Chalky Cortex)
Silicon Dioxide (SiO2)
Quartz (Milky/Crystalline variety)
Silicon Dioxide (SiO2)
Quartz Mineral
Silicon Dioxide (SiO2)
Onyx Marble (Banded Calcite)
Calcite (Calcium Carbonate, CaCO3)
Quartz
Silicon Dioxide (SiO2)
Blue Calcite
Calcium Carbonate (CaCO3)
Quartz
Silicon dioxide (SiO2)
Honey Calcite (Yellow Calcite)
Calcium Carbonate (CaCO3)
Conglomerate
Conglomerate (clastic sedimentary rock)
Citrine Quartz
Silicon Dioxide (SiO2)
Optical Calcite (Iceland Spar)
Calcite (Calcium Carbonate, CaCO3)
Red Garnet
Almandine and Pyrope (Silicate minerals: Fe3Al2(SiO4)3 and Mg3Al2(SiO4)3)
Topaz
Topaz (Al2SiO4(F,OH)2)