Mineraloid (Human Made Geological Specimen)

Tumbled milky quartz pebble

Quartz (silicon dioxide, SiO₂)

Seashell Fragment

Calcium carbonate (CaCO3) - primarily Aragonite or Calcite

Tumbled quartz-rich stone (likely milky quartz/quartzite)

Quartz (SiO₂), possibly quartzite with minor iron-oxide staining

Limonite (Ironstone)

Limonite (mixture of hydrated iron(III) oxide-hydroxides)

Concrete-embedded rock fragment, likely weathered granite or gneiss

Probable granitic silicate assemblage: quartz, feldspar, and dark mica/amphibole

Tumbled yellow jasper

Microcrystalline quartz (chalcedony), SiO₂, colored by iron oxides

Flint / Chert

Microcrystalline Quartz (SiO2)

Purple glassy pebble, possibly slag glass

Unidentified; likely man-made glass rather than a natural mineral

Possible iron-rich chert or flint fragment

Microcrystalline quartz (SiO₂), likely hematite/goethite-bearing

Possible weathered iron-rich rock or slag fragment

Indeterminate; likely limonite/goethite-bearing material, possibly iron slag

Tumbled purple quartz, possibly amethyst

Quartz (SiO₂), likely pale amethyst or lavender quartz

Tumbled rose quartz (probable)

Quartz, silicon dioxide (SiO₂), pink variety

Tumbled chalcedony (likely pale agate or quartz pebble)

Microcrystalline silica, SiO₂ (chalcedony; possibly quartz-rich agate)

Opalite

Synthetic glass (SiO2 + impurities)

Opalite

Synthetic Glass / Man-made Opal Simulant

Obsidian (volcanic glass), likely black obsidian

Rhyolitic volcanic glass; predominantly amorphous SiO₂

Quartzite

Metamorphic Quartzite (SiO2)

Tumbled quartz-rich stone, possibly quartzite

Quartzite (mostly SiO₂), visually similar to chert or weathered quartz sandstone

Polished white chalcedony or quartz pendant

Microcrystalline quartz (chalcedony), SiO₂; exact identification is uncertain from the image

Chert / Flint

Microcrystalline Quartz (SiO2)

Mahogany Obsidian

Volcanic Glass with Hematite (SiO2 + Fe2O3)

Likely metallic meteorite fragment

Undetermined; possibly an iron meteorite or stony-iron meteorite

Green aventurine (likely)

Quartzite dominated by quartz (SiO₂), colored by fuchsite mica or other chromium-bearing inclusions

Polished dark stone, likely basalt or slag-like volcanic rock

Probable fine-grained basalt (plagioclase–pyroxene; possibly glassy volcanic material)

Tumbled milky quartz (likely)

Quartz, silicon dioxide (SiO₂)

Ethiopian Opal (Welo Opal)

Hydrated Amorphous Silica (SiO2·nH2O)

Gemstone-set silver jewelry piece

Likely mixed faceted gemstones in a silver-colored metal setting; stones may include sapphire, ruby/garnet, and yellow sapphire or citrine, but the image is insufficient for species-level identification.

Obsidian

Obsidian (Volcanic Glass)

Blue Impression Jasper beads

Impression jasper (microcrystalline quartz/chalcedony), chiefly SiO₂, with iron-oxide and other mineral inclusions

Tumbled quartz-rich pebble

Quartz (SiO₂), likely with iron-oxide staining and minor inclusions

Tumbled green aventurine (probable)

Quartz, SiO₂, with fuchsite or other mica inclusions

Rose quartz (tumbled)

Quartz, silicon dioxide (SiO₂), pink variety

Tumbled rose quartz

Quartz, silicon dioxide (SiO₂), pink variety

Concrete-like limestone or cemented carbonate rock

Likely limestone (calcium carbonate, CaCO₃); exact identification is uncertain from the image

Possible sea glass (naturally frosted glass), not a confirmed geological specimen

Man-made silicate glass; composition varies, commonly soda-lime glass

Chert (varieties include Flint and Mudstone)

Microcrystalline Silica (SiO2)

Blue gemstone bead bracelet, likely lapis lazuli or dyed stone

Uncertain from image; possible lazurite-bearing lapis lazuli (Na₃Ca(Si₃Al₃)O₁₂S) or dyed quartz/glass imitation

Flint (or Chert)

Microcrystalline quartz (SiO2)

Worked flint (chert) flake or tool

Microcrystalline quartz (SiO₂), commonly called flint or chert

Tumbled chalcedony or quartz pebble

Microcrystalline quartz, SiO₂ (likely chalcedony; exact identification requires testing)

Weathered sandstone or iron-stained quartzite

Quartz-rich sandstone (SiO₂), possibly weakly metamorphosed to quartzite

Weathered limestone or concrete-like calcareous rock

Limestone; predominantly calcite (CaCO₃), possibly containing dolomite and silicate impurities