Antropogenic (Man Made Glass Byproduct)

Polished black stone, likely black obsidian

Obsidian (volcanic glass), primarily silica-rich rhyolitic composition

Orbicular rhyolite (likely)

Rhyolite, a silica-rich volcanic rock; commonly quartz, alkali feldspar, plagioclase, and iron-rich alteration minerals

Sandstone

Sandstone (lithified arenite/wacke)

Chert (Flint)

Chert (microcrystalline quartz)

Chert (or Flint)

Silicon dioxide (SiO2)

Polished black stone pendant, likely obsidian

Volcanic glass; primarily silica-rich rhyolitic glass (SiO₂), if obsidian

Chalcedony (likely iron-stained agate)

Microcrystalline quartz, SiO₂ (chalcedony/agate)

Blue chalcedony (likely common blue agate)

Microcrystalline quartz, SiO₂; chalcedony variety

Pale rounded quartz-rich pebble, likely quartzite

Quartzite (mostly microcrystalline SiO₂), possibly quartz-rich sandstone or vein quartz

Likely weathered quartz-rich stone

Probably quartz-bearing sandstone or milky quartz; exact identification requires testing

Tumbled green aventurine

Quartzite dominated by quartz (SiO₂), with green mica/fuchsite inclusions

Chalcedony (River or Beach Pebbles)

Chalcedony (Silicon Dioxide, SiO2)

Flint

Silicon Dioxide (SiO2) - Microcrystalline Quartz / Chert

Chert (Gravel)

Silicon Dioxide (SiO2)

Chert (Brown Variety)

Microcrystalline Quartz (SiO2)

Amethyst

Silicon Dioxide (SiO2)

Geode (Unopened)

Quartz Geode (SiO2) / Chalcedony Concretion

Weathered quartz-rich rock, possibly milky quartz or quartz-bearing granite

Quartz (SiO₂), potentially with feldspar and iron-oxide staining

Pegmatitic pink feldspar–quartz rock

Granitic pegmatite; chiefly microcline/orthoclase feldspar (KAlSi₃O₈), quartz (SiO₂), and minor mica

Quartz-rich translucent pebble, possibly iron-stained quartz or chalcedony

Quartz (SiO₂), potentially microcrystalline quartz (chalcedony)

Mother of Pearl (Nacre)

Calcium Carbonate (primarily aragonite, with conchiolin)

Quartzite

Quartzite (SiO2)

Chert (Gravel)

Chert (Cryptocrystalline silicon dioxide, SiO2)

Iron-stained quartz or quartz-rich rock

Quartz (SiO₂), likely milky quartz with hematite/goethite staining

Worn quartz-rich pebble, likely chert or quartzite

Microcrystalline quartz (SiO₂), possibly quartzite

Tumbled amber-like chalcedony or resinous fossil material

Likely chalcedony (microcrystalline SiO₂), though the appearance could also indicate copal/amber

Chert (Arrowhead/Tool Grade)

Microcrystalline Quartz (SiO2)

Gemstone Ring

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

Marble

Marble (metamorphosed limestone/dolostone). Predominantly composed of Calcite (CaCO3) for marble derived from limestone, or Dolomite (CaMg(CO3)2) for marble derived from dolostone.

Yellow chalcedony (likely citrine or iron-stained quartz)

Microcrystalline quartz, SiO₂; yellow coloration likely from iron oxides or included quartz varieties

Blue-green fluorite (probable)

Fluorite, calcium fluoride (CaF₂)

Purple fluorite (likely cubic crystal aggregate)

Fluorite, calcium fluoride (CaF₂)

Likely weathered quartz or quartz-rich pebble

Quartz, silicon dioxide (SiO₂)

Mixed Gemstone Beaded Jewelry

Various minerals (e.g., Quartz varieties like Rose Quartz, Amethyst; Peridot; Garnet; etc.)

Mahogany Obsidian

Volcanic Glass with Hematite/Magnetite inclusions (SiO2)

Tumbled quartz (likely milky quartz)

Quartz, silicon dioxide (SiO₂)

Likely porphyritic granite or granitic pegmatite fragment

Quartz–feldspar–mica granitoid; exact identification requires testing

Chert (Flint) with Limestone Coating

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

Tumbled green aventurine

Quartzite dominated by quartz (SiO₂), with green fuchsite mica inclusions

Pink granite or pink feldspathic rock

Granite, chiefly quartz, potassium feldspar, and plagioclase; exact identification is uncertain from the image

Amethyst quartz cluster

Quartz, SiO₂; purple color caused mainly by iron-related defects and irradiation

Amethyst cluster

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