Tumbled black stone, likely black obsidian
Obsidian — natural volcanic glass, primarily SiO₂
Category
Browse organic mineraloid and mineral specimens identified by the Rock Identifier community.
Tumbled black stone, likely black obsidian
Obsidian — natural volcanic glass, primarily SiO₂
Obsidian
Volcanic Glass (SiO2)
Obsidian
Volcanic Glass (predominantly SiO2, approximately 70% or more)
Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Boulder Opal
Hydrated Silica (SiO2·nH2O)
Obsidian
Volcanic Glass (Amorphous Silica)
Black Obsidian
Obsidian (Volcanic Glass)
Snowflake Obsidian
Volcanic Glass with Spherulite Inclusions (70–75% SiO2)
Mahogany Obsidian
Volcanic glass (SiO2 with Hematite or Magnetite inclusions)
Tumbled amber-like gemstone
Likely amber (fossilized resin; organic mineraloid), possibly citrine or yellow-brown glass imitation
Limonite with Quartz (Gossan)
Hydrated iron(III) oxide-hydroxide mixture (FeO(OH)·nH2O) with Silicon Dioxide (SiO2)
Cobalt Glass Slug (Man-made Glass)
Amorphous Silica with Cobalt Oxide (SiO2 + CoO)
Mahogany Obsidian
Volcanic Glass with Hematite/Magnetite inclusions
Black obsidian
Volcanic glass; predominantly silica-rich, noncrystalline SiO₂
Obsidian
Volcanic Glass (felsic composition)
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
Obsidian
Volcanic glass
Obsidian
Volcanic Glass (Silicon Dioxide with impurities)
Common Opal with Host Rock
Opal (Hydrated silica, SiO2·nH2O)
White Precious Opal
Hydrated Silica (SiO2·nH2O)
Precious Opal
SiO2·nH2O (Hydrated Silicon Dioxide)
Obsidian
Obsidian (Volcanic Glass)
Limonite (Yellow Ochre)
Limonite (an amorphous mixture of hydrated iron oxides, primarily FeO(OH)·nH2O)
Limonite (Ironstone) Concretion
FeO(OH)·nH2O (Hydrous ferric oxide)
Snowflake Obsidian
Volcanic glass containing Spherulitic Cristobalite (SiO2)
Common Opal in Host Rock
Hydrated Silica (SiO2·nH2O)
Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Bumblebee Jasper
Anhydrite-Aragonite mixture with Orpiment and Realgar
Opal (Precious Opal)
Hydrated Silica (SiO2·nH2O)
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Pearl (Biogenic Mineraloid)
Calcium carbonate (CaCO3) primarily as Aragonite
Cullet Glass (Man-made Glass Slag)
Amorphous Silica (SiO2) with chemical additives
Obsidian (black volcanic glass)
Obsidian; predominantly rhyolitic volcanic glass, mainly SiO₂ with minor feldspar, quartz, and iron oxides
Likely obsidian (rough fragment)
Volcanic glass, predominantly silica-rich rhyolitic composition (SiO₂-rich, noncrystalline)
Obsidian
Volcanic Glass (Amorphous SiO2)
Mahogany Obsidian
Obsidian (volcanic glass with hematite/magnetite inclusions)
Fire Opal (in Matrix)
Hydrated Silica (SiO2·nH2O)
Mahogany Obsidian
Volcanic glass (Silicon Dioxide with Hematite/Magnetite inclusions)
Snowflake Obsidian
Spherulitic Volcanic Glass (SiO2 + impurities)
Black Opal (Triplet)
Hydrated Silica (SiO2·nH2O)
Obsidian
Obsidian (Volcanic Glass)
Obsidian (Black Obsidian)
Obsidian (Volcanic Glass)