Concretion
Sedimentary Concretion (e.g., Siderite or Ironstone)
sedimentary
Category
Meteorite
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Peridot in Basalt
Olivine ((Mg, Fe)2SiO4) in Basalt
mineral
Diamond
Diamond (pure carbon, C)
mineral
Olivine (Peridot)
Magnesium Iron Silicate (Mg, Fe)2SiO4
mineral
Sandstone Concretion
Clastic Sedimentary Concretion (primarily SiO2 with Fe2O3 cement)
sedimentary
Moldavite
SiO2 (+ Al2O3, FeO, K2O) - Natural Tektite Glass
gemstone
Peridot (Gem-quality Olivine)
Magnesium Iron Silicate ((Mg, Fe)2SiO4)
mineral
Peridot (Olivine)
(Mg, Fe)2SiO4
gemstone
Concretion or weathered iron-rich nodule
Likely an ironstone/siderite–goethite concretion; exact identification requires testing
sedimentary
Iron-Nickel Meteorite (Possible Chondrite or Oxidized Iron)
Siderite (Nickel-Iron) or Chondrite (Si/Fe composite)
igneous
Ironstone Concretion
Ironstone (Siderite/Goethite/Hematite matrix)
sedimentary
Iron Slag
Ferrous Slag (Industrial Byproduct)
mineraloid (anthropogenic byproduct)
Pumice (likely basaltic pumice/scoria)
Vesicular volcanic rock, commonly basaltic; mainly plagioclase, pyroxene, and volcanic glass
igneous
Polished vesicular basalt (likely iron-rich volcanic rock)
Basalt, predominantly plagioclase–pyroxene–olivine; surface may include iron-oxide minerals or metallic-looking infill
igneous
Gold Nugget
Native Gold (Au)
mineral
Concretion
Calcareous/Siliceous Concretion
sedimentary
Peridot (Olivine)
Olivine ((Mg, Fe)2SiO4)
mineral
Slag (Industrial Glassy Byproduct)
Ferro-silicate Slag
Anthropogenic / Non-Natural
Olivine (Peridot)
Magnesium Iron Silicate ((Mg, Fe)2SiO4)
mineral
Concretion
Sedimentary Concretion
sedimentary
Olivine in Basalt (Peridotite Xenolith)
Forsterite-rich Olivine (Mg2SiO4) in Aphanitic Basalt
igneous
Olivine (Peridot)
Magnesium Iron Silicate (Mg,Fe)2SiO4
mineral
Olivine (Peridot)
Magnesium Iron Silicate (Mg,Fe)2SiO4
mineral
Peridot (Olivine)
Magnesium Iron Silicate (Mg, Fe)2SiO4
mineral
Moissanite
Silicon Carbide (SiC)
mineral
Unidentified brown rock fragment
Indeterminate from image; likely a weathered iron-rich lithic fragment
igneous, sedimentary, metamorphic, mineral, gemstone, fossil, or meteorite
Peridot
Olivine ((Mg,Fe)2SiO4)
gemstone
Silicon Carbide (Carborundum)
Moissanite (SiC), though mostly synthetic
mineral
Ironstone Concretion
Ironstone (Siderite/Limonite/Goethite)
sedimentary
Ironstone Concretion
Ferruginous Concretion (Fe2O3·nH2O)
sedimentary
Ironstone Concretion (Boxwork)
Siderite-Limonite Concretion (FeO(OH)·nH2O)
sedimentary
Silicon Carbide (Carborundum)
Silicon Carbide, SiC
mineral
Olivine (Peridotite)
(Mg, Fe)2SiO4 (Magnesium Iron Silicate)
igneous
Olivine Peridotite
Peridotite (comprising Olivine (Mg,Fe)2SiO4 and Pyroxene)
igneous
Olivine (Peridotite)
(Mg,Fe)2SiO4 (Magnesium Iron Silicate)
igneous
Ironstone Concretion
Siderite or Hematite Concretion
sedimentary
Olivine (Peridot)
Magnesium Iron Silicate (Mg,Fe)2SiO4
Mineral
Sandstone Concretion
Ferruginous Sandstone Concretion (Primarily SiO2 with Iron Oxide cement)
sedimentary
Ironstone Concretion
Siderite or Ferruginous Concretion (FeCO3 or Iron Oxides)
sedimentary
Olivine (Peridotite/Dunite)
Olivine (Mg,Fe)2SiO4 within Peridotite
igneous
Slag (Industrial Byproduct)
Artificial silicate/iron byproduct
Mineral description (Anthropogenic material)
Ironstone Concretion / Limonite
Goethite and Limonite (FeO(OH)·nH2O)
sedimentary