Mineral (Man Made Glass, Not Natural)

Obsidian

Obsidian (volcanic glass), predominantly amorphous SiO₂

Tumbled jasper or chert

Microcrystalline quartz (SiO₂), possibly iron-bearing jasper

Tumbled brecciated jasper

Silica-rich microcrystalline quartz/chalcedony (SiO₂), with iron-oxide and other mineral inclusions

Quartz Pebble

Silicon Dioxide (SiO2)

Dyed Howlite (simulating Lavender/Purple Jade or Charoite)

Howlite: Ca2B5SiO9(OH)5 (when natural)

Blue cabochon gemstone, likely sapphire

Corundum (Al₂O₃), blue variety colored mainly by iron and titanium

Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Amethyst

Quartz (Silicon Dioxide with Iron impurities), SiO2

Tree Agate

Chalcedony (SiO2)

Smoky Quartz with Hematite Inclusions

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

Smoky Quartz

Smoky Quartz (Silicon Dioxide, SiO2)

Quartzite

Quartzite (SiO2)

Green Aventurine

Silicon Dioxide (SiO2) with Fuchsite inclusions

Aventurine Quartz

Silicon dioxide with inclusions (KAl2(AlSi3O10)(OH,F)2)

Amethyst (Tumbled Cabinet Stone)

Silicon Dioxide (SiO2) with iron impurities

Chert

Microcrystalline quartz (SiO2)

Tumbled red jasper

Jasper, microcrystalline quartz (SiO₂) colored mainly by iron oxides

Breccia

Breccia

Amethyst

Amethyst (variety of Quartz, SiO2)

Amethyst (Chevron or Banded Amethyst)

Silicon Dioxide (SiO2 with iron impurities)

Amethyst

Amethyst (Silicon Dioxide, SiO2 with Iron impurities)

Citrine (Heat-Treated Amethyst)

Silicon Dioxide (SiO2)

Polished yellow jasper or opaque chalcedony bead

Microcrystalline quartz (SiO₂), likely iron-oxide-stained jasper

Amethyst (Quartz Cluster)

Silicon Dioxide (SiO2) with iron impurities

Amethyst cluster

Quartz, SiO₂; purple coloration is caused mainly by iron-related defects and natural irradiation

Massive Quartz (Yellow/Citrine variety)

Silicon Dioxide (SiO2)

Magnetite (Iron Ore)

Magnetite (Fe3O4)

Jadeite and Mixed Gemstones (Ruby, Sapphire, Emerald)

Jadeite (NaAlSi2O6), Corundum (Al2O3), Beryl (Be3Al2(Si6O18))

Limonite or Ironstone Nodule

Hydrated iron oxide-hydroxide (FeO(OH)·nH2O)

Blue Topaz (facetted in jewelry)

Aluminum silicate fluoride hydroxide (Al2SiO4(F,OH)2)

Tumbled brown stone, likely tiger’s-eye or jasper

Quartz-rich microcrystalline silica, likely SiO₂ (possible tiger’s-eye; identification uncertain from image)

Vesicular volcanic rock, likely weathered pumice or scoria

Pumice/scoria; predominantly volcanic glass and feldspar, with possible iron oxides

Citrine Quartz Cluster

Silicon Dioxide (SiO2)

Septarian Pebble

Septarian nodule / Concretion

Rough Green Adventurine

Aventurine (Variety of Quartz, SiO2)

Sandstone (Yellow/Tan)

Clastic sedimentary rock (primarily SiO2 with iron oxide staining)

Limonite Ironstone

Goethite-Limonite concretion / Iron oxide

Limonite with Quartz

Hydrated Iron Oxide Hydroxide, FeO(OH)·nH₂O with SiO₂

Limonite with Quartz

Hydrated Iron Oxide Hydroxide with Silicon Dioxide (FeO(OH)·nH2O + SiO2)

Raw Corundum (Sapphire/Ruby variant)

Aluminum oxide (Al2O3)

Granite

Intrusive Igneous Rock

Amethyst

Silicon Dioxide (SiO2) with trace Iron impurities