Obsidian
Volcanic Glass (SiO2 + impurities)
Category
Browse mineraloid (organic) specimens identified by the Rock Identifier community.
Obsidian
Volcanic Glass (SiO2 + impurities)
Fulgurite
Fulgurite (Lechatelierite)
Black Obsidian
Volcanic Glass (SiO2 + impurities)
Honey-colored amber (possibly copal)
Amber: fossilized tree resin, an organic mineraloid; composition varies, mainly carbon, hydrogen, and oxygen
Polished amber
Amber (fossilized plant resin), commonly succinite; organic mineraloid rather than a true mineral
Amber
Succinite (Resinite)
Tumbled black stone, likely black obsidian
Obsidian — volcanic glass, primarily SiO₂
Gold Sheen Obsidian
Volcanic Glass (SiO2 + Fe3O4 / Gas Inclusions)
Polished amber
Amber (fossilized plant resin), commonly succinite; organic mineraloid rather than a true mineral
Tumbled amber-like gemstone
Likely amber (fossilized resin; organic mineraloid), possibly citrine or yellow-brown glass imitation
Obsidian
Volcanic glass
Limonite (Ironstone)
Limonite (mixture of hydrated iron oxides, primarily Goethite α-FeO(OH))
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
White Opal
Hydrated Silica (SiO2·nH2O)
Probable amber fragment
Amber (fossilized plant resin; chiefly amorphous organic resin, commonly dominated by succinite)
Obsidian
Volcanic Glass (Amorphous SiO2)
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)
Fulgurite
Fulgurite (Lechatelierite-rich fused silica)
Limonite (Iron Ore)
Limonite (Hydrated Iron Oxide, FeO(OH)·nH2O)
Amber
Succinite (specifically for Baltic amber); Approximate formula: C10H16O
Obsidian
Volcanic Glass (70% or more SiO2)
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Obsidian
Obsidian (Amorphous volcanic glass, predominantly SiO2)
Obsidian
Volcanic glass
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Limonite (Iron Ore)
Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)
Pearl (Biogenic Mineraloid)
Calcium carbonate (CaCO3) primarily as Aragonite
Precious Opal
Hydrated Silica (SiO2·nH2O)
Limonite/Ironstone
Limonite (FeO(OH)·nH2O)
Green Opal
Hydrated Silica (SiO2·nH2O)
Black Obsidian
Obsidian (Volcanic Glass, SiO2 + impurity)
Limonite (Iron Ore)
Limonite (an amorphous mixture of hydrated iron oxides, primarily FeO(OH)·nH2O)
Likely obsidian (possibly tektite or slag glass)
Volcanic glass; primarily SiO₂, noncrystalline
Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
Jet
Lignite (Anthracite-grade compact coal)
Obsidian
Volcanic Glass (SiO2)
Amber (likely a small polished amber piece)
Natural fossil resin; amber is an organic mineraloid, not a crystalline mineral. The image alone cannot confirm authenticity.
Orange cabochon gemstone, likely amber or amber-like resin
Natural amber: fossilized plant resin (organic mineraloid), commonly succinite; exact identification requires testing
Common opal in iron-stained host rock
Opal (hydrated amorphous silica, SiO₂·nH₂O), likely common opal
Obsidian (black volcanic glass), possibly slag or basalt
Obsidian; chiefly amorphous volcanic silica glass, approximately SiO₂-rich rhyolitic composition