Tufa Rock and Tumbled Gemstones
Calcareous Tufa (Calcium Carbonate, CaCO3)
sedimentary
Category
Mineral (Man Made Glass, Not Natural)
Browse mineral (man made glass, not natural) specimens identified by the Rock Identifier community.
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Tumbled jasper or quartzite pebble
Jasper (microcrystalline quartz, SiO₂), possibly iron-stained quartzite
metamorphic
Quartz (likely Jasper or Chert variety)
Quartz (SiO₂)
Mineral
Peacock Ore (Bornite or Iridescent Chalcopyrite)
Bornite (Cu5FeS4) or Chalcopyrite (CuFeS2) with tarnish
mineral
Black Onyx
Chalcedony (Silicon Dioxide, SiO2)
gemstone
Amethyst cluster
Quartz, silicon dioxide (SiO₂), purple variety colored mainly by iron impurities and irradiation
gemstone
Smoky Quartz
Silicon Dioxide (SiO2)
mineral
Granite
Granite (phaneritic intrusive igneous rock consisting mainly of quartz, alkali feldspar, and plagioclase)
igneous
Chert Nodule
Microcrystalline Quartz (SiO2)
sedimentary
Amethyst
Silicon dioxide (SiO2) with iron impurities
mineral
Aura Quartz (Titanium/Bismuth Coated)
Silicon Dioxide (SiO2) with metallic vapor coating
mineral
Oco Geode
Silicon Dioxide (SiO2) with various inclusions
mineral
Agate Geode
Microcrystalline Quartz (SiO2)
mineral
Agate (Carnelian / Chalcedony pebble)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
mineral
Carnelian / Agate
Silicon Dioxide (SiO2) - Chalcedony variety
mineral
Tumbled chalcopyrite (likely)
Chalcopyrite, CuFeS₂
mineral
Ferruginous Sandstone Pebble
Iron-rich Clastic Sedimentary Rock
sedimentary
Stalagmite (Flowstone)
Speleothem (Calcium Carbonate, CaCO3)
sedimentary
Red Jasper (Quartz)
SiO2 (Silicon Dioxide with Iron Oxide inclusions)
sedimentary
Peacock Ore (Chalcopyrite)
Chalcopyrite (CuFeS2)
mineral
Dyed or color-enhanced agate/microcrystalline quartz bead
Chalcedony (microcrystalline SiO₂), likely agate
gemstone
Limonite (Iron Stone/Goethite)
Limonite (mixture of hydrated iron oxides, primarily Goethite: α-FeO(OH))
mineral
Tumbled green jasper (probable serpentine-rich stone)
Jasper, microcrystalline quartz (SiO₂), possibly mixed with serpentine or chlorite
mineral
Blue Topaz (Cut Gemstone)
Aluminum silicate fluoride hydroxide (Al2SiO4(F,OH)2)
gemstone
Sandstone (likely Quartzose Sandstone)
Arenite (primarily SiO2)
sedimentary
Raw Diamond
Diamond (pure Carbon, C)
mineral
Common Marble
Calcium Carbonate (CaCO3)
metamorphic
Ruby (in costume jewelry context)
Corundum (Al2O3) with Chromium impurities
mineral
Chert (Jasper/Common Opal mix)
Microcrystalline Quartz (SiO2)
sedimentary
Green Garden Quartz (Phantom Quartz)
Silicon Dioxide (SiO2) with Chlorite inclusions
mineral
Granite Pebble
Granite (Phaneritic intrusive igneous rock)
igneous
Aura Quartz (Coated Quartz)
Silicon Dioxide (SiO2) coated with vaporized metals
mineral
Lapis Lazuli
Lapis Lazuli (a rock type, not a single mineral, composed primarily of lazurite, calcite, and pyrite)
Mineral, part of a rock
Quartzite (River Pebbles)
Metamorphosed Sandstone (SiO2)
metamorphic
Dyed Pink Quartzite (Jadeite Simulant)
Silicon Dioxide (SiO2) with organic dye
metamorphic
Dark river-worn cobble, possibly basalt or fine-grained volcanic rock
Likely basaltic rock; exact identification requires a fresh surface and tests
igneous
Sapphire
Corundum (Al2O3)
gemstone
Likely polished basalt with pale mineral inclusions
Basalt; inclusions possibly calcite, quartz, or weathered feldspar
igneous
Tiger’s eye
Chatoyant quartz (fibrous quartz pseudomorph after crocidolite), SiO₂
gemstone
Satin Spar (Gypsum)
Gypsum (Satin Spar variety) - CaSO4·2H2O
mineral
Quartzite
Quartzite (chiefly SiO2)
metamorphic
Citrine Quartz
Silicon Dioxide (SiO2)
mineral