Glass

Blue glass-like gemstone, likely synthetic spinel or glass

Uncertain; possibilities include synthetic cobalt-blue spinel (MgAl₂O₄) or cobalt-colored glass

Quartz (likely milky quartz or quartz glass-like fragment)

Quartz, silicon dioxide (SiO₂)

Slag (Industrial Glass Slag)

Amorphous Silica / Ferro-silicate Slag

Obsidian

Volcanic Glass (70-75% SiO2)

Sea Glass

Man-made silicate glass

Slag Glass

Silicon dioxide with impurities

Quartz

Silicon Dioxide (SiO2)

Opalite

Synthetic Glass (Simulated Opal)

Opalite

Man-made opalized glass

Smoky Quartz

Silicon Dioxide (SiO2)

Faceted clear gemstone ring

Likely colorless quartz (SiO₂); the photo does not establish the stone’s identity

Slag

Industrial Silicate Slag

Tumbled amber-colored mineral or glassy pebble

Uncertain; likely chalcedony/quartz, possibly resinous amber or slag glass

Tumbled milky quartz

Quartz (silicon dioxide, SiO₂), microcrystalline or massive variety

Sea Glass

Man-made vitreous material / Silicon dioxide

Sea Glass

Man-made silicate glass

Sea Glass

Man-made silicate glass

Sea Glass

Man-made vitreous material

Sea Glass

Man-made silicate glass weathering product

Sea Glass

Silicon dioxide (mostly)

Sea Glass

Man-made silicate glass

Sea Glass

Amorphous silicon dioxide (Man-made glass weathered by nature)

Sea Glass

Amorphous silicon dioxide (SiO2) - Man-made glass tumbled by nature

Sea Glass

Man-made vitreous material

Slag Glass

Anthropogenic Amorphous Silicon Dioxide

Quartz-rich pegmatite specimen

Hydrothermal/pegmatitic quartz aggregate, chiefly SiO₂, with probable feldspar and mica/accessory sulfides

Quartz Drusy on Matrix

Silicon Dioxide (SiO2)

Fluorescent glassy mineral specimen, possibly hyalite opal

Hyalite (hydrated amorphous silica, SiO₂·nH₂O), tentative

Milky quartz pebble

Quartz (silicon dioxide, SiO₂)

Clear quartz crystal (likely quartz bead/specimen)

Quartz, silicon dioxide (SiO₂)

Cut quartz crystal (likely rock crystal)

Quartz, silicon dioxide (SiO₂), trigonal crystal system

Quartz in Matrix (possibly with Biotite or Hornblende)

Quartz (Silicon Dioxide, SiO2) in Granitic Matrix

Quartz (specifically Milky or Clear Quartz fragment)

Silicon Dioxide (SiO2)

Green glassy gemstone-like specimen

Likely synthetic glass or treated quartz; exact identification requires testing

Quartz-rich rock, likely milky quartz or quartzite

Quartz (SiO₂), possibly in a quartzite or hydrothermal vein matrix

Quartz

Silicon Dioxide (SiO2)

Milky Quartz with Limonite

Silicon Dioxide (SiO2)

Polished chalcedony (likely moss or dendritic agate)

Microcrystalline quartz, SiO₂; chalcedony with possible iron-oxide and/or manganese dendrites

Tumbled green aventurine (likely)

Quartz variety, SiO₂, colored by fuchsite or other chromium-bearing mica

Orange chalcedony / carnelian with drusy quartz

Microcrystalline quartz, SiO₂ (chalcedony; iron-colored variety often called carnelian), with possible calcite or quartz matrix

Mica (Biotite or Phlogopite variety)

Phyllosilicate (complex mineral formula involving K, Mg, Fe, Al, Si, and O)

Obsidian

Volcanic Glass (SiO2 - Silicon Dioxide with impurities)