Fossilized Wood (Petrified Wood)
Silicified Wood (primarily quartz/chalcedony replacing organic matter)
Sedimentary (with some aspects of mineral replacement)
Category
Organic Gemstone (Not A Mineral)
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Dalmatian Stone (commonly Dyed)
Dalmatian Jasper (Peralkaline igneous rock)
igneous
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Spinel
Magnesium Aluminum Oxide (MgAl2O4)
mineral
Blue Apatite
Apatite (Group), Ca5(PO4)3(F,Cl,OH)
mineral
Green Banded Chert (Agate/Jasper)
Silicon Dioxide (SiO2) with trace impurities of Chlorite or Glauconite
sedimentary
Fuchsite (Green Muscovite in Quartz)
Chromium-rich Muscovite (K(Al,Cr)2(AlSi3O10)(OH)2)
metamorphic
Banded Agate
Cryptocrystalline Quartz (SiO2)
mineral
Moonstone (Feldspar variety)
Orthoclase Feldspar (KAlSi3O8)
mineral
Blue Apatite
Fluoroapatite (Ca5(PO4)3F)
mineral
Obsidian
Volcanic Glass (predominantly SiO2)
igneous
Hematite
Iron(III) oxide (Fe2O3)
mineral
Green Aventurine
Silicon Dioxide (SiO2) with inclusions of Fuchsite
metamorphic
Tiger's Eye (Jasper-like Chalcedony)
Silicon dioxide (SiO2) - Pseudomorph after Crocidolite
metamorphic
Quartz (Microcrystalline Fragment)
Silicon Dioxide (SiO2)
mineral
Black Tourmaline
Schorl (NaFe3Al6(BO3)3Si6O18(OH)4)
mineral
Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Jasper
Silicon dioxide (SiO2) with iron oxide inclusions
sedimentary
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Hematite
Iron(III) oxide (Fe2O3)
mineral
Stichtite in Serpentine (Atlantisite)
Mg6Cr2CO3(OH)16·4H2O (Stichtite) within Mg3Si2O5(OH)4 (Serpentine)
Metamorphic
Obsidian
Obsidian (Volcanic Glass)
igneous
Aventurine
Silicon Dioxide (SiO2) with inclusions
metamorphic
Peridot
Olivine (Magnesium Iron Silicate - (Mg, Fe)2SiO4)
Mineral
Orange Calcite
Calcium Carbonate (CaCO3)
mineral
Smoky Quartz
Silicon Dioxide (SiO2) with natural radiation treatment
mineral
Black Spinel
Magnesium Aluminum Oxide (MgAl2O4)
mineral
Moonstone (specifically Cat's Eye or Gray Moonstone)
Orthoclase (Potassium Aluminum Silicate) with the formula (K,Na)AlSi3O8
mineral
Red Jasper (River pebble)
Jasper (Silicon Dioxide, SiO2 plus iron oxide impurities)
mineral
Amethyst (Tumbled/Polished)
Silicon Dioxide (SiO2) with iron impurities
mineral
Rough Diamond
Diamond (pure Carbon, C)
mineral
Garnet (Almandine)
Almandine (Fe3Al2(SiO4)3)
mineral
Rhodonite (in matrix)
Rhodonite (Mn,Fe,Mg,Ca)SiO3
Mineral
Diamond
Native Carbon (C)
mineral
Tiger's Eye
Tiger's Eye (Pseudomorph of Quartz after Crocidolite), SiO2
mineral
Smoky Quartz
Smoky Quartz (Silicon Dioxide, SiO2)
mineral
Carnelian (Red Chalcedony)
Silicon Dioxide (SiO2)
mineral
Amethyst
Silicon Dioxide (SiO2) with iron impurities
mineral
Carnelian Agate (with Quartz/Chalcedony)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
mineral
Quartz / Quartzite
Silicon Dioxide (SiO2)
minerals
Olivine in Basalt (Peridot)
Magnesium Iron Silicate (Mg,Fe)2SiO4 (Mineral) within Basalt (Rock)
igneous
Rhodonite
Manganese Silicate (Mn,Fe,Mg,Ca)SiO3
mineral