Mineraloid (Human Made Geological Specimen)

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

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

Tumbled quartz-rich pebble

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

Worked flint (chert) flake or tool

Microcrystalline quartz (SiO₂), commonly called flint or chert

Seashell Fragment

Calcium carbonate (CaCO3) - primarily Aragonite or Calcite

Tumbled green aventurine (probable)

Quartz, SiO₂, with fuchsite or other mica inclusions

Quartz (Pebble)

Quartz (SiO₂)

Flint (or Chert)

Microcrystalline quartz (SiO2)

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

Polished brown river pebble, likely quartzite

Quartzite (mostly microcrystalline SiO₂), identification tentative from appearance

Weathered sandstone or iron-stained quartzite

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

Blue-gray stone pebble (possibly slag or a weathered rock)

Unidentified fine-grained rock; composition cannot be determined from the image

Obsidian

Volcanic Glass (Amorphous Silicon Dioxide)

Likely metallic meteorite fragment

Undetermined; possibly an iron meteorite or stony-iron meteorite

Limonite (Ironstone)

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

Milky Quartz

Silicon Dioxide (SiO2)

Obsidian (black volcanic glass), possibly slag or basalt

Obsidian; chiefly amorphous volcanic silica glass, approximately SiO₂-rich rhyolitic composition

Sandstone (Red/Brown Variety)

Arenite (composed primarily of SiO2 with Fe2O3 iron oxide inclusions)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Polished white chalcedony or quartz pendant

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

Obsidian (volcanic glass), likely black obsidian

Rhyolitic volcanic glass; predominantly amorphous SiO₂

Green Glass Cullet / Recycled Glass

Amorphous Silicon Dioxide (SiO2) with various metal oxides

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Opalite

Synthetic glass (SiO2 + impurities)

Common Opal in Host Rock

Hydrated Silica (SiO2·nH2O)

Weathered limestone or concrete-like calcareous rock

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

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.

Iron-rich sandstone or lateritic rock

Ferruginous sandstone; predominantly quartz (SiO₂) cemented or stained by iron oxides/hydroxides

Pink calcite (likely)

Calcite — calcium carbonate, CaCO₃

Mahogany Obsidian

Volcanic Glass with Hematite (SiO2 + Fe2O3)

Amber / Copal

Succinite (fossilized resin)

Polished brown agate or jasper

Microcrystalline quartz, SiO₂ (chalcedony variety; exact identification uncertain)

Rounded gray-brown pebble

Indeterminate; likely weathered quartz-rich sandstone or fine-grained volcanic rock

Agate

Silicon Dioxide (SiO2) - Cryptocrystalline Chalcedony

Quartz (Microcrystalline/Chert)

Silicon Dioxide (SiO2)

Tumbled chalcedony (likely carnelian/agate)

Microcrystalline quartz, SiO₂; chalcedony, with possible iron-oxide coloring

Chert / Flint

Microcrystalline Quartz (SiO2)

Tumbled carnelian/chalcedony

Microcrystalline quartz (SiO₂), iron-oxide-stained chalcedony

Obsidian

Obsidian (Volcanic Glass)

Sandstone Concretion

Sedimentary Concretion (Quartz sandstone with iron oxide cement)

Amber / Copal

Succinite (fossilized tree resin)