Tektite (Natural Glass)

Flint or chert

Microcrystalline quartz (SiO₂), likely gray chert/flint

Likely polished dark stone or glassy mineral bead

Indeterminate; possibly obsidian, hematite, or a dark agate

Blue slag glass or dyed glass-like industrial material

Amorphous silicate glass; likely copper-bearing blue slag, but possibly colored man-made glass

Amethyst and Rose Quartz Jewelry

Silicon Dioxide (SiO2)

Citrine Quartz

Silicon Dioxide (SiO2)

Strawberry Quartz

Silicon Dioxide with Hematite inclusions (SiO2 + Fe2O3)

Black obsidian

Volcanic glass (mostly rhyolitic silica glass; SiO₂-rich)

Chert / Flint

Cryptocrystalline quartz (SiO2)

Blue sea glass or blue glassy mineral fragment

Uncertain; likely man-made soda-lime glass, not a natural mineral

Slag Glass (Cullet Glass)

Amorphous Silica (Industrial byproduct)

Sea Glass

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

Sandstone

Arenite (SiO2 primarily)

Tumbled goldstone-like quartz pebble

Likely iron-stained quartz or jasper; exact identification requires testing

Black onyx or black agate bead necklace

Microcrystalline quartz, SiO₂ (likely chalcedony/black agate; possibly dyed)

Tumbled green aventurine (likely)

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

Quartz (Citrine / Yellow Quartz)

Silicon Dioxide (SiO2)

Blue cabochon gemstone ring

Uncertain; likely blue sapphire (corundum, Al₂O₃), blue topaz, or synthetic glass/spinel

Beads (likely glass or man-made material)

N/A (artificial material)

Quartzite

SiO2 (Silicon Dioxide / Metamorphic Quartz)

Quartz Pebble

Silicon Dioxide (SiO2)

Green glassy cabochon, likely dyed or synthetic material

Uncertain; possibly green obsidian, chrysoprase, or synthetic glass

Cut quartz crystal (likely rock crystal)

Quartz, silicon dioxide (SiO₂), trigonal crystal system

Small rounded quartz-rich pebble

Likely quartz-bearing chert or weathered quartzite; exact identification requires testing

Sandstone

Arenite (primarily SiO2, silica)

Quartz (Citrine variety)

Silicon Dioxide (SiO2)

Yellow Quartz (Citrine Quartz)

Silicon Dioxide (SiO2)

Colorless faceted gemstone (most likely synthetic cubic zirconia)

Cubic zirconia, ZrO₂ (likely synthetic); natural alternatives include quartz or diamond

Blue glassy fragment among beach gravel

Likely cobalt-blue man-made glass; not a natural mineral specimen

Yellow faceted gemstone, likely citrine or synthetic glass

Citrine (quartz, SiO₂) is the leading natural possibility; visual identification is uncertain from the photograph

Purple faceted gemstone, likely amethyst or synthetic colored corundum

Amethyst: quartz (SiO₂); possible alternative: purple corundum (Al₂O₃) or glass

Blue cabochon gemstone, likely synthetic glass or dyed stone

Indeterminate from image; possible glass, synthetic spinel, sodalite, or lapis lazuli

Green Fluorite (likely synthetic or heat-treated for jewelry)

Calcium Fluoride (CaF2)

Tumbled amethyst

Amethyst, purple quartz (SiO₂)

Goldstone

Aventurine glass

Tumbled citrine or yellow quartz

Quartz, silicon dioxide (SiO₂); likely iron-colored citrine, possibly heat-treated amethyst

Quartz fragment

Quartz (silicon dioxide, SiO₂), likely milky or smoky quartz

Opalite

Synthetic Opalised Glass

Sandstone

Arenite (Siliclastic sedimentary rock)

Diamond (or Simulant)

Carbon (C)

Tumbled citrine quartz

Quartz, silicon dioxide (SiO₂); citrine is yellow iron-related quartz

Tumbled black stone, likely obsidian

Obsidian (volcanic glass; predominantly SiO₂)

Obsidian (black volcanic glass)

Obsidian; silica-rich volcanic glass, typically rhyolitic to dacitic composition