Sandstone (Quartzose)
Arenite (SiO2 principal composition)
sedimentary
Category
Man Made Material, Not A Natural Rock Or Mineral Specimen
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Porphyritic granite or granodiorite
Coarse-grained plutonic rock composed mainly of quartz (SiO₂), feldspar, and mica/amphibole
igneous
Pea Gravel / River Gravel
Unconsolidated Clastic Sedimentary Aggregate
sedimentary
Basalt Pebble
Basalt (Mafic volcanic rock)
igneous
Rough Sapphire (possibly Yellow/Green Corundum)
Corundum (Al2O3)
mineral
Garnet-bearing granite or pegmatitic granitic rock
Coarse-grained granitoid, likely granite or pegmatite, composed mainly of quartz and feldspar with almandine/spessartine garnet and dark biotite or amphibole
igneous
Bauxite
Bauxite (Al(OH)3, γ-AlO(OH), and α-AlO(OH))
sedimentary
River Stone (Basalt or Siltstone)
Basalt (extrusive igneous rock) or fine-grained Siltstone
igneous
Granite Cobble
Granite (Phaneritic igneous rock)
igneous
Tumbled granite or granitic pebble
Granite; primarily quartz, feldspar, and mica (exact variety uncertain from the image)
igneous
Amethyst
Silicon dioxide with iron impurities (SiO2:Fe3+)
mineral
Milky Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Pink Quartzite
Metamorphosed Quartz Arenite (SiO2)
metamorphic
Corundum
Corundum (Al2O3)
Mineral
Diamond
Carbon (C)
mineral
Granite Pebble
Granite (High-silica plutonic rock)
igneous
Likely polished black stone or obsidian
Obsidian (volcanic glass), chiefly SiO₂
igneous
Basalt
Basalt
igneous
Chert
Chert (Microcrystalline Quartz)
sedimentary
Quartz (in a rock matrix)
Quartz (SiO2)
mineral
Dyed Quartz Geode
Dyed crystalline quartz (Silicon Dioxide, SiO2)
mineral
Tumbled yellow jasper (likely serpentine or calcite-rich stone)
Jasper: microcrystalline quartz (SiO₂); exact yellow veining may indicate serpentine, calcite, or iron oxides
mineral
Aquamarine
Beryl (Be3Al2Si6O18 with iron impurities)
mineral
Smoky Quartz
Smoky Quartz (Silicon Dioxide, SiO2)
mineral
Amethyst
Silicon Dioxide (SiO2) with iron impurities
mineral
Diamond
Carbon (C)
mineral
Diamond (or Diamond Simulant/Cubic Zirconia)
Carbon (C) - if diamond, or Zirconium dioxide (ZrO2) - if Cubic Zirconia
mineral
Rounded river or beach pebble
Likely quartz-rich sandstone or quartzite; exact identification requires a close-grained view and hardness test
sedimentary
Chert / Flint
Silicon Dioxide (SiO2)
sedimentary
Smoky Quartz (Polished)
Silicon Dioxide (SiO2)
mineral
Smoky Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Pumice
Pumice (Vitreous volcanic rock)
igneous
Sandstone or Mudstone
Sedimentary Rock
sedimentary
Basalt River Stone
Basalt
igneous
Metallic sulfide mineral fragment, likely bornite or chalcopyrite
Bornite (Cu₅FeS₄) or chalcopyrite (CuFeS₂)
mineral
Kidney Stone
Calcium Oxalate (CaC2O4), Uric Acid, or Struvite
mineral
Granite
Intrusive Igneous Rock
igneous
Chert (Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Geode (Unopened)
Quartz Geode (SiO2) / Chalcedony Concretion
mineral
Basalt with Quartz Vein
Mafic volcanic rock with hydrothermal SiO2 filling
igneous
Sandstone
Arenite (primarily SiO2 with trace Fe2O3)
sedimentary
Weathered quartz-rich rock, likely milky quartz or quartzite
Quartz (SiO₂), possibly quartzite with iron-oxide staining
mineral