Glass

Sea Glass

Amorphous Silica (SiO2) with various additives

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Amethyst Quartz fragment

SiO2 (Silicon Dioxide with Iron impurities)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Quartz (Drusy/Crystalline)

Silicon Dioxide (SiO2)

Blue goldstone (man-made glass)

Copper-bearing aventurine glass; synthetic silicate glass

Sea Glass

Amorphous Silicon Dioxide (SiO2)

Sea Glass

Man-made silicate glass

Chert (Flint) with Limestone Coating

Silicon Dioxide (SiO2) with Calcium Carbonate (CaCO3) cortex

Clear Quartz

Silicon Dioxide (SiO2)

Likely polished dark stone or glassy mineral bead

Indeterminate; possibly obsidian, hematite, or a dark agate

Clear Quartz

Silicon Dioxide (SiO2)

Prasiolite (Green Quartz) / Sea Glass Amalgam

SiO2 (Silicon Dioxide)

Tumbled opalite (likely synthetic glass)

Opalite; typically man-made opalescent soda-lime glass, not a recognized mineral species

Green glass sphere/marble

Soda-lime glass (primarily SiO2, Na2O, CaO)

Blue obsidian-like volcanic glass

Volcanic glass, chiefly silica-rich amorphous material (composition uncertain)

Sea Glass (Turquoise/Aqua)

Amorphous Silica (SiO2) with transition metal dopants

Tumbled opalite (likely man-made glass)

Opalite glass; a synthetic opalescent glass, not a natural mineral species

Small tumbled quartz-like pebble

Likely quartz (SiO₂), possibly milky quartz or pale chalcedony

Chert (Fossiliferous Chert/Flint)

Silicon Dioxide (SiO2)

Glass / Silicon Dioxide (Man-made)

SiO2 (Amorphous Silicon Dioxide)

Snowflake Obsidian

Volcanic glass with Cristobalite inclusions (mostly SiO2)

Obsidian

Obsidian (principally SiO2 - Silicon Dioxide)

Amethyst and Green Aventurine (Tumbled Gemstones set in a wand)

Quartz (SiO2) varieties - Amethyst and Aventurine

Chert (Flint)

Chert (SiO2)

Chert (often called Flint when dark)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Black Obsidian

Volcanic Glass (Silica glass with magnetite/hematite microcrystals)

Silver Sheen Obsidian

Volcanic Glass (Silicate glass with microscopic gas bubbles)

Polished black stone, likely black obsidian

Obsidian (volcanic glass), predominantly rhyolitic silica glass

Polished black stone, likely black obsidian

Obsidian (volcanic glass), primarily rhyolitic silica glass

Sea Glass

Anthropogenic Silicate Glass

Blue glass-like bead or gemstone keychain ornament

Indeterminate; likely cobalt-blue glass or synthetic blue spinel, not identifiable as a natural mineral from the image

Quartz (Grain)

Silicon Dioxide (SiO2)

Green glass-like mineral specimen, likely fluorite

Fluorite (calcium fluoride, CaF₂), if natural; appearance may also indicate colored glass

Opalite Egg

Synthetic Glass (Simulated Opal)

Green obsidian (likely molded or heat-treated glass-like specimen)

Volcanic glass; predominantly rhyolitic composition (silica-rich amorphous SiO₂)

Likely polished milky quartz pebble

Quartz, silicon dioxide (SiO₂)

Snowflake Obsidian

Volcanic Glass (spherulitic obsidian)

Moldavite (rough fragment)

Natural impact glass, chiefly SiO₂ with Al₂O₃ and trace oxides; tektite

Gemstone Ring

Various (Likely Glass, Cubic Zirconia, or assorted semi-precious stones)

Blue chalcedony cabochon (probable)

Chalcedony, a cryptocrystalline variety of quartz; silicon dioxide, SiO₂

Goldstone

Man-made glass with copper inclusions