Sandstone (Yellow/Tan)
Clastic sedimentary rock (primarily SiO2 with iron oxide staining)
sedimentary
Category
Synthetic Or Natural Fiber
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Porphyritic Basalt (Chinese Writing Stone)
Porphyritic Basalt with Feldspar Phenocrysts
igneous
Amethyst
Silicon Dioxide (SiO2) with iron impurities
mineral
Smoky Quartz
Silicon Dioxide (SiO2) with aluminum impurities and natural irradiation
mineral
Smoky Quartz with Siderite and Pyrite
Silicon Dioxide (SiO2) with Ferrous Carbonate (FeCO3) and Iron Sulfide (FeS2)
mineral
Carnelian
Carnelian (SiO2 with Iron Oxide impurities)
mineral
Jasper Chert
Microcrystalline Quartz (SiO2) with iron oxide inclusions
sedimentary
Diorite (or salt-and-pepper granite pebble)
Phaneritic Igneous Rock (Intermediate Composition)
igneous
Amethyst
Silicon Dioxide with trace Iron (SiO2 + Fe3+)
mineral
Smoky Quartz
Smoky Quartz (SiO2 - Silicon Dioxide with aluminum impurities)
mineral
Heat-Treated Amethyst (Commercial Citrine)
Silicon Dioxide (SiO2) - Macro-crystalline Quartz
mineral
Green Aventurine
Silicon Dioxide (SiO2) with Fuchsite inclusions
metamorphic
Boulder Opal
Precious Opal in Ironstone (Amorphous Hydrated Silica, SiO2·nH2O)
Mineral
Asphalt (Bituminous Concrete)
Bituminous mix containing aggregates and petroleum-based binder (CnH2n+2)
not a rock (anthropogenic material/technofossil)
Diamond in Gold Setting
Diamond (C - pure carbon)
mineral
Black Tourmaline in Quartz and Feldspar Matrix
Schorl (NaFe3Al6(BO3)3Si6O18(OH)4) with Quartz and Feldspar
igneous
Cubic Zirconia (in Jewelry)
Zirconium Dioxide (ZrO2)
mineral
Amethyst Quartz (Tumbled)
Amethyst (Silicon Dioxide with iron impurities, SiO2)
mineral
Apache Tear
Hydrated Obsidian (Natural Volcanic Glass)
igneous
Dyed Agate Geode Slice
Silicon Dioxide (SiO2)
mineral
Garnet (Almandine/Pyrope series)
Garnet Group - X3Y2(SiO4)3
mineral
Herkimer Diamond
Quartz (SiO2)
mineral
Diamond (in Gold Jewelry)
Carbon (C)
mineral
Diamond (set in Gold)
Carbon (C)
mineral
Smoky Quartz
Silicon Dioxide (SiO2)
mineral
Kyawthuite
Kyawthuite (Bi3+Sb5+O4)
mineral
Basalt River Cobble
Basalt (Aphanitic Mafic Volcanic Rock)
igneous
Gold Nugget
Native Gold (Au)
mineral
Bornite
Copper Iron Sulfide (Cu5FeS4)
mineral
Bornite
Bornite (Cu5FeS4)
mineral
Smoky Quartz
Silicon Dioxide (SiO2)
mineral
Smoky Quartz and Chalcedony Geode Fragment
Silicon Dioxide (SiO2)
mineral
Banded Agate (River Stone)
Agate (Silicon Dioxide - SiO2)
mineral
Unidentifiable Rock Fragment
Uncertain
Pink Banded Agate (Dyed)
Chalcedony (cryptocrystalline silica), chemical formula SiO2
mineral
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Diamond (set in Gold)
Diamond (pure carbon, C)
mineral
Pink Quartz (likely dyed)
Silicon Dioxide (SiO2)
mineral
Gold Nugget
Native Gold (Au)
mineral
Amethyst
Silicon Dioxide (SiO2) with trace Iron (Fe) impurities
mineral
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide)
Igneous
Obsidian (Apache Tear)
Obsidian / Amorphous Volcanic Glass (main component: SiO2)
igneous