Basalt

Diabase (Greenstone)

Diabase (Dolerite)

Rhyolite

Rhyolite (Extrusive Igneous Rock)

Amethyst and Peridot

Amethyst (SiO2 with iron impurities) and Peridot ((Mg, Fe)2SiO4)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Amethyst

SiO2 (Silicon Dioxide with iron impurities)

Blue Chalcedony

Chalcedony (cryptocrystalline Silicon Dioxide - SiO2)

Druzy Quartz on Milky Quartz

Silicon Dioxide (SiO2)

Moss Agate

Chalcedony (SiO2) with dendritic inclusions of Manganese or Iron oxide

Ruby

Corundum (mineral species), variety: Ruby (Al2O3 with Cr3+ as the chromophore)

Ruby

Corundum (Al2O3:Cr)

Pink Sapphire

Corundum (Al2O3 with trace Chromium and Iron)

Amethyst Quartz

Silicon Dioxide (SiO2 with iron impurities)

Greenstone

Metamorphosed Mafic Igneous Rock

Carnelian Agate

Silicon Dioxide (SiO2) with Ferric Oxide (Fe2O3) inclusions

Labradorite (a variety of Feldspar)

Labradorite; (Na,Ca)(Al,Si)4O8 (a plagioclase feldspar)

Lava Rock (Scoria)

Scoria (highly vesicular basaltic rock)

Granite with Mafic Inclusions

Granite (Phaneritic igneous rock composed of Quartz, Feldspar, and Mica)

Lake Superior Agate

Silicon Dioxide (SiO2) - Variety Agate

Eclogite

Eclogite (comprising Omphacite and Garnet)

Amethyst

Silicon Dioxide (SiO2) with Fe3+ impurities

Carnelian

Carnelian (variety of Chalcedony, SiO2)

Botryoidal Black Chalcedony Geode (Black Grape Agate)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Chlorastrolite (Greenstone)

Chlorastrolite (variety of Pumpellyite) - Ca2(Mg,Fe)Al2(SiO4)(Si2O7)(OH)2 · H2O

Ruby

Corundum (Al2O3 with Chromium trace impurities)

Greenschist / Migmatite

Regional Metamorphic Complex (Facies: Greenschist to Amphibolite)

Amethyst Geode (polished heart-cut)

Silicon Dioxide (SiO2) with iron impurities

Amethyst

Amethyst (Silicon Dioxide - SiO2 with iron impurities)

Amethyst

SiO2 (Silicon Dioxide with Iron impurities and natural radiation influence)

Amethyst (Faceted)

Silicon Dioxide (SiO2) with iron impurities

Lake Superior Agate

Banded Chalcedony (Silicon Dioxide / SiO2)

Larimar

Blue Pectolite (NaCa2Si3O8(OH))

Amethyst

Amethyst (variety of Quartz, SiO2)

Amethyst

SiO2 (Silicon Dioxide) - Purple variety of Quartz

Chevron Amethyst

Silicon Dioxide (SiO2) with trace Iron (Fe3+)

Montana Moss Agate

Chalcedony (Silicon Dioxide, SiO2)

Scoria (Lava Rock)

Mafic extrusive volcanic rock (Scientific formula varies based on mineral content: primarily SiO2, MgO, and FeO)

Chlorastrolite (Isle Royale Greenstone)

Chlorastrolite (Pumpellyite-(Mg,Fe2+): Ca2MgAl2(Si2O7)(SiO4)(OH)2∙H2O)

Agate (specifically Lace Agate or Banded Agate)

Silicon Dioxide (SiO2)

Scoria (Lava Rock)

Scoria (Extrusive Igneous Rock / Mafic Silicates)

Olivine-bearing Basalt / Scoria

Mafic Igneous Rock (primarily (Mg, Fe)2SiO4)

Carnelian Agate

Silicon Dioxide (SiO2) - Variety: Chalcedony

Banded Agate (Tumbled)

Agate (Silicon Dioxide, SiO2 - Cryptocrystalline Quartz)