Chalcedony (or a variety of Chalcedony, likely Agate or Jasper)
Chalcedony (SiO₂)
Category
Browse mineral (or mineraloid if microcrystalline) specimens identified by the Rock Identifier community.
Chalcedony (or a variety of Chalcedony, likely Agate or Jasper)
Chalcedony (SiO₂)
Limonite (Ironstone)
Limonite (mixture of hydrated iron oxides, primarily Goethite α-FeO(OH))
Limonite (Iron Stone/Ocher)
Limonite (FeO(OH)·nH2O)
Limonite (Iron Ore)
FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide mixture)
Limonite/Goethite Concretion
Hydrated Iron(III) Oxide-hydroxide (FeO(OH)·nH2O)
Limonite (Iron Stone/Goethite)
Limonite (mixture of hydrated iron oxides, primarily Goethite: α-FeO(OH))
Limonite (Ironstone Concretion)
Limonite (Hydrated iron(III) oxide-hydroxide, mixtures of FeO(OH)·nH2O)
Pearl (Biogenic Mineral)
Calcium Carbonate (primarily Aragonite) with Conchiolin; CaCO3
Limonite (Iron Ore/Sandstone mixture)
Limonite (FeO(OH)·nH2O) often mixed with Goethite and sedimentary matrix
Limonite Concretion
Hydrated iron(III) oxide-hydroxide (FeO(OH)·nH2O)
Native Sulfur
Sulfur (S8)
Pearl
Calcium Carbonate (Aragonite) with Conchiolin; formula: CaCO3
Quartzite with Iron Inclusions
Quartzite (pre d om i n a n t l y SiO2) with H e m a t i t e / G o e t h i t e
Pearl (Biogenic Mineraloid)
Calcium carbonate (CaCO3) primarily as Aragonite
Limonite with Quartz (Gossan)
Hydrated iron(III) oxide-hydroxide mixture (FeO(OH)·nH2O) with Silicon Dioxide (SiO2)
Amber
Succinite (Organic Mineraloid)
Black Pearl (Tahitian Pearl)
Aragonite / Calcite (CaCO3) with Conchiolin
Obsidian
Volcanic glass (SiO2 + impurities)
Limonite or Ironstone Nodule
FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide)
Black Obsidian
Volcanic Glass (predominantly SiO2)
Black Obsidian
Volcanic Glass (Amorphous SiO2 with trace impurities)
Pearl
Aragonite / Calcium Carbonate (CaCO3)
Obsidian
Volcanic Glass (Amorphous silicon dioxide with impurities)
Black Obsidian
Volcanic glass
Obsidian
Volcanic Glass
Obsidian
Volcanic Glass (SiO2 + impurities)
Black Obsidian
Volcanic Glass (SiO2 + impurities)
Black Obsidian
Volcanic Glass (predominantly SiO2, Silicon Dioxide)
Tumbled black stone, likely black obsidian
Obsidian — volcanic glass, primarily SiO₂
Gold Sheen Obsidian
Volcanic Glass (SiO2 + Fe3O4 / Gas Inclusions)
Mahogany Obsidian
Volcanic glass (high silica) with inclusions of Magnetite or Hematite
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Conch Pearl
Calcareous concretion (CaCO3)
Obsidian
Volcanic Glass (Amorphous SiO2)
Limonite (Iron Ore)
Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)
Obsidian
Volcanic Glass (SiO2 rich)
Polished mahogany obsidian (probable)
Volcanic glass; chiefly rhyolitic silica-rich glass (SiO₂), compositionally near rhyolite
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
Limonite (Iron Ore)
Limonite (Hydrated Iron Oxide, FeO(OH)·nH2O)
Pearl
Calcium carbonate (CaCO3) - mainly Aragonite with Conchiolin
Pearl
Aragonite / Calcium Carbonate (CaCO3)
Obsidian
Volcanic Glass (70% or more SiO2)