Amethyst
Silicon Dioxide (SiO2) with iron impurities
mineral
Category
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Obsidian
Volcanic Glass (predominantly SiO2)
igneous
Pearl
Calcium Carbonate (CaCO3) - mainly Aragonite and Calcite
mineral
Green Onyx (Banded Calcite)
Banded Calcite / Aragonite (CaCO3)
mineral
Yellow Jasper
Silicon Dioxide (SiO2) with iron hydroxides (Goethite)
sedimentary
Amethyst (Quartz)
Amethyst (SiO2 with iron impurities)
mineral
Banded Calcite (often sold as 'Mexican Onyx')
Calcium Carbonate (CaCO3)
sedimentary
Limonite with Hematite
Limonite (FeO(OH)·nH2O) and Hematite (Fe2O3)
mineral
Aragonite (Banded Calcite / 'Mexican Onyx')
Aragonite (Calcium Carbonate - CaCO3)
mineral
Limonite (Iron Ore)
Limonite (an FeO(OH)·nH2O mineraloid, not a true mineral due to variable composition)
Mineral
Petrified Wood
Silicified Wood (primarily SiO2)
sedimentary
Yellow Jasper
Silicon Dioxide (SiO2) with iron oxide inclusions
sedimentary
Pink Halite (Himalayan Salt)
Halite (Sodium Chloride, NaCl)
sedimentary
Yellow Quartz (Citrine Quartz)
Silicon Dioxide (SiO2)
mineral
Blue Calcite
Calcium Carbonate (CaCO3)
mineral
Howlite
Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)
mineral
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Ferruginous Quartz (Iron-stained Quartz)
Silicon Dioxide (SiO2) with Hematite/Limonite impurities
mineral
Tiger's Eye
Silicon dioxide (SiO2) with fibrous inclusions of crocidolite (riebeckite)
Mineral
Obsidian
Volcanic Glass (mostly SiO2)
igneous
Amethyst
SiO2 (Silicon Dioxide with iron impurities)
mineral
Laterite
Laterite (primarily composed of hydrated oxides of iron and aluminum)
Sedimentary Rock (as a residual soil/rock, it's often considered a type of sedimentary rock due to its formation from weathering, though it can cross into soil science)
Amazonite
Amazonite (Microcline) - K(AlSi3O8)
mineral
Quartzite
Quartzite (primarily SiO2)
Metamorphic
Amethyst
Silicon Dioxide (SiO2) with iron impurities
mineral
Limonite (Ironstone)
Limonite (FeO(OH)·nH2O)
mineral
Amethyst
SiO2 (Silicon Dioxide)
Mineral
Anthracite Coal
Anthracite (Carbon-rich metamorphic coal)
sedimentary
Jasper
Silicon Dioxide (SiO2)
sedimentary
Yellow Jasper
Silicon Dioxide (SiO2) with Goethite/Iron oxide impurities
sedimentary
Rose Quartz
Silicon Dioxide (SiO2)
mineral
Septarian Nodule
Septarian Concretion (CaCO3 + CaMg(CO3)2)
sedimentary
Quartz (Milky Quartz)
Silicon Dioxide (SiO2)
mineral
Banded Calcite (often sold as 'Green Onyx')
Calcite (Calcium Carbonate, CaCO3)
sedimentary
Obsidian
Volcanic Glass (Amorphous Silica)
igneous
Chert (specifically Flint Arrowhead)
Silicon dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Epidote in Quartz
Quartz with Epidote inclusions (SiO2 with Ca2(Al,Fe)3(SiO4)3(OH) inclusions)
Mineral
Obsidian
Obsidian (Volcanic Glass, SiO2)
igneous
Moss Agate
SiO2 (Silicon Dioxide) with dendritic inclusions
Mineral
Green Aventurine
Silicon Dioxide (SiO2) with Chromium-rich Fuchsite mica
mineral
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
igneous
Limonite (Iron Ore)
Limonite (FeO(OH)·nH2O)
mineral