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Obsidian

Extrusive igneous volcanic glass (rich in SiO2)

Coarse-grained Granite (Quartz and Feldspar dominated)

Granitoid (KAlSi3O8 – NaAlSi3O3 – CaAl2Si2O8 – SiO2)

Petrified Wood

Silicified Wood (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Celestite (Celestine) Geode

Strontium Sulfate (SrSO4)

Banded Chert or Agate

Silicon Dioxide (SiO2)

Green Fluorite

Fluorite (Calcium Fluoride, CaF2)

Sandstone Pebble (Quartzite-rich)

Clastic Terrigenous Sedimentary Rock (SiO2 dominant)

Quartzite (or Milky Quartz pebble)

Quartzite (primarily Silicon Dioxide, SiO2)

Blue Topaz (specifically London Blue shade)

Topaz - Al2SiO4(F,OH)2

Quartz Vein in Sedimentary Rock

Silicon Dioxide (SiO2) with host Chert or Limestone

Orange Calcite

Calcite (CaCO3)

Tree Agate

Silicon Dioxide (SiO2)

Bumblebee Jasper (technically Bumblebee Stone)

Calcite, Aragonite, and Realgar/Orpiment mixture (SiO2 + CaCO3 + As2S3/As2S2)

Hematite

Iron(III) oxide (Fe2O3)

Portable Ceramic Space Heater

Polished Acrylonitrile Butadiene Styrene (ABS) Plastic with Ceramic Heating Elements

Tree Agate

Dendritic Agate (Silicon Dioxide, SiO2)

Sandstone (Quartzose Sandstone)

Clastic Terrigenous Sedimentary Rock (primarily SiO2)

Rhodonite

Manganese Silicate (Mn,Fe,Mg,Ca)SiO3

Ferruginous Quartz (Iron-stained Quartz)

Silicon Dioxide (SiO2) with iron oxide inclusions (Limonite/Hematite)

Sandstone (Picture Sandstone)

Arenite (primarily SiO2 with iron oxide impurities)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Rose Quartz

Silicon Dioxide (SiO2) with trace impurities of titanium, iron, or manganese

Jasper with Hematite inclusions

Silicon Dioxide (SiO2) with Ferric Oxide (Fe2O3)

Banded Agate (specifically Sardonyx or Carnelian Agate)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Dyed Chalcedony (Agate)

Silicon Dioxide (SiO2) with artificial pigment

Chert (Grey-Green Var.)

Silicon Dioxide (SiO2)

Copper-bearing Quartz (likely Malachite on Quartz matrix)

Cu2CO3(OH)2 (Malachite) on SiO2 (Quartz)

Amethyst

SiO2 (Silicon Dioxide)

Amazonite

Potassium Feldspar (KAlSi3O8)

Chert (specifically Jasper or Flint type)

Microcrystalline Quartz (SiO2)

Blue Crackle Quartz (Dyed Quarzite)

Silicon Dioxide (SiO2) with artificial dye

Granite

Granite (Mainly Quartz, Feldspar, and Mica)

Agate (specifically, multi-colored or pastel-dyed agate)

Silicon dioxide (SiO2) - specifically, a cryptocrystalline variety of quartz known as Chalcedony, with banding classified as Agate. (If it were Fluorite, the chemical formula would be Calcium Fluoride - CaF2).

Garnet Schist

Almandine Garnet Schist

Rose Quartz

Silicon Dioxide (SiO2) with traces of titanium, iron, or manganese

Fossiliferous Limestone (Coral Fossil)

Scleractinian Coral in Calcium Carbonate (CaCO3)

Petrified Wood

Silicified Wood (SiO2)

Carnelian

Carnelian (a variety of Chalcedony, SiO2)

Fluorite (often referred to casually as 'Fluorspar' in industrial contexts)

Fluorite (CaF2)

Quartz

Silicon Dioxide (SiO₂)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)