Ironstone Concretion
Siderite or Limonite Concretion (FeCO3 or FeO(OH)·nH2O)
sedimentary
Category
Industrial Byproduct (Often Mistaken For Obsidian Or Mineral)
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Ironstone (Limonite/Goethite Concretion)
Ferruginous Sedimentary Rock (composed of Goethite FeO(OH) and Limonite)
sedimentary
Lapis Lazuli
Lapis Lazuli (Primary mineral: Lazurite, (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)
metamorphic
Epidote (or Epidote-rich rock)
Epidote. Mineral formula: Ca2(Al,Fe)3(SiO4)3(OH).
Mineral, often found in metamorphic rocks but also in sedimentary and igneous rocks
Mahogany Obsidian
Volcanic glass (Silicon Dioxide with Hematite/Magnetite inclusions)
igneous
Serpentinite
Serpentinite; predominantly serpentine-group minerals, commonly with magnetite, talc, and carbonate
metamorphic
Obsidian Arrowhead
Volcanic Glass (70% or more SiO2)
Igneous
Ironstone Concretion (Coprolite-like)
Goethite/Hematite Siderite Spheroid (FeCO3 or FeO(OH))
sedimentary
Snowflake Obsidian (possibly mixed with Jasper or other matrix)
Obsidian with Cristobalite inclusions
igneous
Muscovite Schist
Muscovite Mica Schist (KAl2(AlSi3O10)(OH)2)
metamorphic
Sandstone (specifically an Iron-Concretion)
Arenite with Iron Oxide (Limonite/Goethite) cementation
sedimentary
Polished black stone, possibly basalt or black jasper
Basalt (fine-grained mafic rock) or microcrystalline quartz if jasper
igneous
Obsidian
Volcanic Glass
igneous
Goldstone
Aventurine Glass (Man-made)
mineral
Black Obsidian
Obsidian (Volcanic Glass)
igneous
Chert / Chalcedony
Silicon Dioxide (SiO2)
sedimentary
Sodalite
Sodalite (Na8Al6Si6O24Cl2)
mineral
Iron-stained Quartz
Silicon Dioxide (SiO2) with Hematite/Limonite impurities
mineral
Sodalite
Na8(Al6Si6O24)Cl2 (Sodium Aluminum Silicate Chloride)
mineral
Fossilized Shark Tooth (Drum Fish Tooth/Pavement Tooth)
Sparidae or Sciaenidae (Crushing plate dental fossil)
fossil
Green Aventurine
Silicon Dioxide (SiO2) with Fuchsite inclusions
mineral
Pyrite on Limestone
Iron Disulfide (FeS2) in Calcium Carbonate (CaCO3) matrix
sedimentary (matrix) / mineral (inclusion)
Siltstone
Siltstone (composed of clastic quartz and feldspar)
sedimentary
Black tumbled stone, likely obsidian
Volcanic glass; chiefly amorphous SiO₂
igneous
Sodalite
Sodalite (Na8Al6Si6O24Cl2)
mineral
Pyrite (Fool's Gold)
Iron Sulfide (FeS2)
mineral
Orange Quartz
Silicon Dioxide (SiO2) with iron oxide inclusions
mineral
Pyrite (Fool's Gold)
Iron Sulfide (FeS2)
mineral
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurities)
igneous
Obsidian
Volcanic Glass (SiO2)
igneous
Sodalite
Sodalite (Na8(Al6Si6O24)Cl2)
mineral
Snowflake Obsidian
Obsidian with Cristobalite inclusions
igneous
Obsidian (Black)
Obsidian (High-silica volcanic glass)
igneous
Mahogany Obsidian
Obsidian (SiO2 + Fe2O3)
igneous
Ironstone Concretion
Ferruginous Sandstone / Hematite-rich Concretion
sedimentary
Quartzite (Iron-stained River Rock)
Metamorphic Rock consisting primarily of Quartz (SiO2)
metamorphic
Goldstone and pink quartz bead strands
Goldstone is aventurescent copper-bearing glass; pink beads are likely rose quartz (SiO₂), though dyed or glass imitations are possible
mineral
Red obsidian (likely mahogany obsidian)
Volcanic glass; primarily silica-rich rhyolitic glass (SiO₂), commonly with iron-oxide inclusions
igneous
Snowflake Obsidian
Volcanic Glass (SiO2 rich with Cristobalite inclusions)
igneous
Obsidian (specifically Mahogany Obsidian)
Volcanic glass (high silica content, SiO2)
igneous
Possibly tumbled black stone (uncertain; may be black glass or obsidian)
Undetermined; possible obsidian (natural volcanic glass, predominantly SiO₂)
mineral
Polished Black Obsidian
Volcanic Glass (70-75% SiO2)
igneous