Grey Agate (Banded Chalcedony)
Agate (Silicon Dioxide - SiO2)
mineral
Category
Sedimentary (Chemically Precipitated Mineral)
Browse sedimentary (chemically precipitated mineral) specimens identified by the Rock Identifier community.
Agate (Sliced Nodule)
Silicon Dioxide (SiO2) - Chalcedony variety
mineral
Amazonite (Green Feldspar)
Microcline (variety Amazonite), Chemical Formula: K(AlSi3O8)
mineral
Dyed Purple Agate
Silicon Dioxide (SiO2) - Cryptocrystalline Quartz
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Porcelain (Kaolin-based)
Alumina silicate ceramic (composed primarily of Kaolinite: Al2Si2O5(OH)4)
metamorphic (man-made/engineered)
Diorite
Diorite (Intermediate intrusive igneous rock)
igneous
Blue Quartzite
Quartzite (primarily SiO2 with inclusions like Dumortierite or Magnesio-riebeckite)
metamorphic
Pyrite
Iron Sulfide (FeS2)
mineral
Chert or Flint (polished/water-worn)
Chert (a microcrystalline or cryptocrystalline variety of quartz, SiO2). Flint is a specific variety of chert.
Sedimentary (most likely, as Chert is a sedimentary rock often found as nodules in limestone or as bedded deposits; however, it can also form by metasomatic replacement, which leans towards metamorphic processes under certain conditions)
Limonite and Goethite encrusted Quartz (Iron-stained Gossan)
FeO(OH)·nH2O (Limonite) / FeO(OH) (Goethite) on SiO2 (Quartz)
mineral
Micaceous Rock (likely Muscovite Schist/Gneiss or a Muscovite-rich Specimen)
Predominantly Muscovite (KAl2(AlSi3O10)(F,OH)2), often found in rocks like Muscovite Schist or Muscovite Gneiss.
Metamorphic, Mineral (within a rock type)
Sandstone
Arenite (SiO2 primarily)
sedimentary
Garnet Beads
Garnet Group (complex nesosilicates, e.g., Almandine Fe3Al2(SiO4)3)
Mineral
Milky Quartz (Water-Worn Pebble)
Quartz (Silicon Dioxide, SiO2)
mineral
Cavansite
Cavansite (Ca(VO)Si4O10·4H2O)
mineral
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Satin Spar (Selenite variant)
Gypsum (Calcium Sulfate Dihydrate, CaSO4·2H2O)
mineral
Quartzite
Quartzite (SiO2)
metamorphic
Quartzite (River Cobble)
Quartzite (predominantly SiO2)
metamorphic
Quartzite (Gold/Tan River Cobble)
Quartzite (composed primarily of crystalline SiO2)
metamorphic
Banded Agate with Druzy Quartz
Agate (Silicon Dioxide - SiO2)
mineral
Orbicular Jasper
Silicon Dioxide (SiO2), variety of Chalcedony
Mineral
Gold Ore
Native Gold (Au) in Matrix
mineral
African Turquoise (Jasper)
Polychrome African Jasper (often marketed as 'African Turquoise' due to its color, but it is not true turquoise)
Rock
Rutilated Quartz
SiO2 with TiO2 inclusions (Rutile)
Mineral
Limonite (Iron Ore)
Limonite (FeO(OH)·nH2O)
mineral
Quartz on Sandstone
Silicon Dioxide (SiO2) in Lithic Sandstone
sedimentary
Limonite / Ironstone Nodule
Limonite (Hydrated iron(III) oxide-hydroxide), FeO(OH)·nH2O
mineral
Orange Calcite (likely polished specimen)
Calcite
Mineral
Fluorite
Fluorite (Calcium Fluoride, CaF2)
mineral
Green Slag Glass
Amorphous Silica Glass (Anthropogenic)
Industrial byproduct (often mistaken for obsidian or mineral)
Quartzite (River Pebble)
Metamorphosed sandstone (SiO2)
metamorphic
Shale
Lutaceous sedimentary rock
sedimentary
Sandstone (Tumbled/River Pebble)
Arenite (composed primarily of SiO2)
sedimentary
Pyrite in Shale
Iron Disulfide (FeS2)
mineral
Red Garnet
Almandine and Pyrope (Silicate minerals: Fe3Al2(SiO4)3 and Mg3Al2(SiO4)3)
mineral
Sandstone
Clastic sedimentary rock (primarily SiO2)
sedimentary
Limonite
Limonite (Hydrous iron oxides, predominantly Goethite FeO(OH)·nH2O)
mineral
Limonite (Iron Ore)
Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)
mineral
Brecciated Jasper
Silicon Dioxide (SiO2) with varying mineral inclusions (Iron Oxide, Hematite, Clay)
sedimentary (clastic/chemical)
Slate
Slate (Foliated metamorphic rock)
metamorphic