Tektite (Natural Glass)

Polished black stone, likely black obsidian

Obsidian (volcanic glass), chiefly SiO₂

Fulgurite

Fulgurite (Lechatelierite-rich variety)

Tumbled blue stone, likely blue aventurine or dyed chalcedony

Aventurine quartz (SiO₂) or chalcedony (microcrystalline SiO₂); exact identification requires testing

Yellow chalcedony (likely citrine-like quartz)

Cryptocrystalline quartz, SiO₂; possibly iron-stained chalcedony or pale citrine

Blue Obsidian

Volcanic Glass (SiO2 with inclusions)

Dyed Quartzite

Tumbled Metamorphosed Quartz (SiO2) with artificial pigment

Black glassy fragment, likely obsidian or industrial glass

Volcanic glass (obsidian), chiefly amorphous SiO₂; identification uncertain from image

Quartz with Iron Stains

Silicon Dioxide (SiO2) with FeOx inclusions

Opalite

Synthetic opalescent glass

Quartz Pebble

Silicon Dioxide (SiO2)

Snowflake Obsidian

Volcanic Glass with Cristobalite inclusions (SiO2)

Ruby (or potential synthetic/imitation)

Corundum (Al2O3)

Amethyst (Rose-tinted variation)

Silicon Dioxide (SiO2) with trace iron impurities

Sandstone

Arenite (SiO2 based)

Sandstone

Arenite

Sandstone

Arenite (SiO2 primarily)

Sandstone (Quartzose)

Arenite (primarily SiO2)

Sandstone

Arenite (SiO2 based)

Likely polished chalcedony or agate cabochon pendant

Microcrystalline quartz, SiO₂ (chalcedony/possibly banded agate)

Amethyst cluster

Quartz, silicon dioxide (SiO₂), purple variety colored mainly by iron impurities and irradiation

Cullet Glass (Slag Glass)

Amorphous Silicon Dioxide (Industrial byproduct)

Opalite

Synthetic glass / Opaque silicious glass

Jasper / Chert (river tumbled)

Microcrystalline Quartz (SiO2)

Obsidian (likely snowflake or volcanic-glass variety)

Volcanic glass, predominantly rhyolitic in composition; mainly SiO₂ with minor Al, Na, K, Fe, and Ca

Orange mineral fragment, possibly citrine or iron-stained quartz

Quartz (SiO₂), tentatively iron-included quartz/citrine

Polished Black Onyx (or Obsidian)

Silicon Dioxide (SiO2)

Tumbled yellow quartz (likely citrine or iron-stained quartz)

Quartz, SiO₂; yellow color from trace iron or irradiation/heat-related coloration

Green Aventurine

Silicon Dioxide (Quartz) with inclusions of Fuchsite (K(Al,Cr)2(AlSi3O10)(OH)2)

Smoky Quartz (with Iron Inclusions)

Silicon Dioxide (SiO2)

Chert / Flint Nodule

Cryptocrystalline quartz (SiO2)

Blue Goldstone

Aventurine Glass (Silicon Dioxide infused with Cobalt/Copper)

Mixed river-worn rock and mineral collection

Mostly quartz/quartzite, feldspar-bearing granitoid, chert, and mafic volcanic rocks; exact species vary by pebble

Chert

Microcrystalline Quartz (SiO2)

White quartz pebble

Quartz (silicon dioxide, SiO₂)

Sandstone or Limestone

Arenite or Calcareous Sedimentary Rock

Sandstone

Arenite (SiO2 primarily)

Citrine (Yellow Quartz)

Silicon Dioxide (SiO2)

Yellow Quartz / Citrine Quartz

Silicon Dioxide (SiO2)

Man-made Crystal (Lead Glass)

Lead oxide-doped Silica Glass (approx. SiO2 + PbO)

Strawberry Quartz (or Sunstone / Tumbled Quartz)

Silicon Dioxide (SiO2) with Hematite/Lepidocrocite inclusions

Goldstone

Aventurine Glass (Man-made glass with copper inclusions)

Yellow Quartz (Citrine Quartz or Yellow Jasper)

Silicon Dioxide (SiO2) with iron impurities