Glass

Fulgurite

Lechatelierite (Silica glass tubes)

Small rough quartz-family crystal specimens, including likely amethyst and citrine

Quartz, silicon dioxide (SiO₂); purple specimen is likely amethyst, yellow specimen likely citrine or iron-stained quartz

Small translucent quartz fragment

Quartz (SiO₂), possibly milky or near-colorless quartz

Quartz-rich granitic rock, possibly weathered pegmatite

Granite or pegmatitic quartz–feldspar aggregate; mainly SiO₂ quartz with K-feldspar/plagioclase and minor mica

Muscovite Mica

Muscovite KAl2(AlSi3O10)(OH)2

Snowflake Obsidian

Volcanic Glass with Spherulitic Cristobalite (SiO2)

Quartz crystal fragment (likely milky quartz)

Quartz, silicon dioxide (SiO₂), trigonal crystal system

Quartz (Milky/Smoky variety)

Silicon Dioxide (SiO2)

Weathered quartz-rich stone, likely milky quartz

Quartz (SiO₂), possibly a quartz-rich metamorphic or igneous fragment

Tumbled quartz pebble

Quartz, silicon dioxide (SiO₂), likely milky quartz

Tumbled smoky quartz

Quartz (SiO₂), likely smoky variety

Amethyst chip or tumbled fragment

Quartz, SiO₂; purple coloration from trace iron and irradiation

Clear quartz sphere or polished quartz cabochon (tentative)

Quartz, silicon dioxide (SiO₂); appearance may also be consistent with ordinary glass, which cannot be ruled out from the image alone

Amethyst (Tumbled Quarz)

Silicon Dioxide (SiO2) with iron impurities

Pale green translucent mineral fragment

Indeterminate; possibly fluorite, calcite, or glassy quartz

Tumbled white quartz (likely milky quartz)

Quartz, silicon dioxide (SiO₂)

Tumbled rose quartz (likely)

Quartz, silicon dioxide (SiO₂), pink variety colored mainly by trace inclusions

Amethyst cabochon ring

Amethyst, purple quartz (SiO₂)

Amethyst (rough crystal fragment)

Quartz, SiO₂; purple coloration from iron impurities and irradiation

Tumbled rose quartz

Rose quartz (pink quartz), silicon dioxide, SiO₂

Goldstone (blue-goldstone–style glass) beads

Artificial aventurine glass, typically silica glass with copper inclusions; not a natural mineral

Tumbled orange jasper or iron-stained quartzite

Jasper: microcrystalline quartz (SiO₂) with iron oxides; possible quartzite

Libyan Desert Glass

Natural Silica Glass (SiO2 with minor iron and titanium)

Snowflake Obsidian

Volcanic Glass with Spherulite inclusions (mainly Cristobalite)

Quartz (Milky/Crystalline variety)

Silicon Dioxide (SiO2)

Likely tumbled white quartz or quartzite pebble

Quartz (SiO₂), possibly quartzite

Flint

Chert (SiO2)

Quartz-bearing metamorphic rock, likely quartzite with dark mica/amphibole

Quartzite or quartz-rich schist; chiefly SiO₂ quartz with biotite, hornblende/amphibole, and iron-oxide staining

Dyed blue banded agate

Microcrystalline quartz (SiO₂), mainly chalcedony

Polished gray pebble, likely quartzite or fine-grained granite

Probable quartzite (mostly microcrystalline SiO₂); identification is uncertain from the photograph

Tumbled green stone, likely serpentine or aventurine

Indeterminate; possible serpentine-group mineral (Mg₃Si₂O₅(OH)₄) or green quartzite/aventurine (SiO₂)

Rounded river cobble, likely quartz-rich sandstone or quartzite

Indeterminate quartz-rich clastic rock; probable sandstone (SiO₂-rich)

Chert (variations include Flint/Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Tan/Yellow variety)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Quartz (Iron-stained)

Silicon Dioxide (SiO2)

Citrine (or Yellow Chalcedony / Quartz)

Silicon Dioxide (SiO2)

Tumbled Rose Quartz

Silicon Dioxide (SiO2)

Quartz with Iron Staining

Silicon Dioxide (SiO2) with Hematite/Limonite inclusions

Chert (Flint)

SiO2 (Microcrystalline Quartz)

Chert

Microcrystalline quartz (SiO2)

Petrified Wood

Silicified Wood (Permineralized organic tissue)

Chalcedony (Common Opal or Agate variant)

Silicon Dioxide (SiO₂)