Natural Pearl
Calcium carbonate (primarily Aragonite and Conchiolin), CaCO3
mineral
Category
Man Made
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Polished brown chalcedony (likely carnelian or jasper)
Microcrystalline quartz, SiO₂; iron oxides produce the brown coloration
mineral
Chert
Silicon dioxide (SiO2)
Sedimentary
Basalt
Basalt
igneous
Fossil Coral
Scleractinia (Stony Coral) fossil
fossil
Likely blue glass or synthetic gemstone jewelry
Uncertain; possibly synthetic spinel, cubic zirconia, or blue glass
gemstone
Sandstone (Quartzose)
Arenite (composed primarily of SiO2)
sedimentary
Sandstone
Arenite (composed primarily of SiO2)
sedimentary
Granite
Phaneritic Felsic Igneous Rock
igneous
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone
Arenite
sedimentary
Granite
Granite (Phaneritic Quartz-Feldspar intrusive rock)
Igneous
Chalcedony / milky quartz flake
Microcrystalline quartz (SiO₂), likely chalcedony; possibly a worked quartzite or chert fragment
mineral
Quartzite
Metamorphic Quartz Sandstone
metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Chert (Cherty Shale / Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Black-and-white agate geode pendant
Agate (microcrystalline quartz, SiO₂), likely a hollow geode slice with chalcedony and drusy quartz
mineral
Red Sandstone
Quartz Arenite (iron-stained) / SiO2
sedimentary
Chert / Flint
Silicon Dioxide (SiO2)
sedimentary
Brecciated Jasper
Brecciated Jasper (Microcrystalline Quartz / SiO2)
sedimentary
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Chalcedony (Agate / Jasper Specimen)
Silicon Dioxide (SiO2)
mineral
Fossilized Coral (Petoskey Stone / Hexagonaria)
Hexagonaria percarinata / Rugosa coral (CaCO3)
fossil
Slate
Metamorphic Pelitic Rock
metamorphic
Chert / Flint
Microcrystalline Quartz (SiO2)
sedimentary
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Flint
SiO2 (Cryptocrystalline Quartz)
sedimentary
Slate
Metamorphic Pelitic Rock
metamorphic
Green Aventurine
Silicon Dioxide (SiO2+KAl2(AlSi3O10)(OH)2)
metamorphic
Granite
Granite (composed primarily of Quartz, Feldspar, and Mica)
igneous
Gabbro
Gabbro (Mg, Fe)2Si2O6 / (Ca, Na)(Al, Si)4O8
igneous
Chert (Chalcedony/Agate variety)
Silicon Dioxide (SiO2)
sedimentary
Chert (with Quartz)
Microcrystalline Quartz (SiO2)
sedimentary
Diamond (in Jewelry)
Carbon (C)
mineral
Asphalt aggregate (crushed stone in bitumen)
Artificial composite; predominantly crushed granite, basalt, limestone, and/or recycled aggregate bound by bitumen
sedimentary
Petoskey Stone / Rugose Coral Fossil
Hexagonaria percarinata
fossil
Blue-green chrysocolla rough specimen
Chrysocolla, hydrated copper aluminosilicate; commonly associated with malachite, quartz, and limonite
mineral
Sandstone (Quartzose)
Arenite (primarily SiO2)
sedimentary
Granite
Granite (Plutonic Igneous Rock)
igneous
Granite
Granite (Silicic Intrusive Igneous Rock)
Igneous
Granite
Granite (Felsic Plutonic Rock)
igneous
Granite
Granite (phaneritic intrusive igneous rock consisting of quartz, feldspar, and mica)
igneous