Not A Natural Rock

Conglomeratic concrete or asphalt aggregate surface with dark bituminous chunks

Polymictic gravel aggregate; dark pieces likely bitumen/asphalt, not a natural rock

Mixed rock specimens; likely pink feldspar/quartz and a dark, mica-bearing rock

Tentative visual identification: pink K-feldspar–quartz-rich granite/pegmatite fragments and a dark amphibole- or biotite-rich metamorphic rock; exact identification is uncertain from the image

Smoky Quartz

Silicon Dioxide (SiO2)

Small dark gray stone, possibly slate or basalt

Unidentified fine-grained rock; image is insufficient for confident identification

Goldstone (aventurine glass)

Synthetic copper-bearing soda-lime glass; commonly sold as red goldstone

Likely pale limestone or calcite-rich rock

Calcite-bearing limestone; chiefly calcium carbonate (CaCO₃)

Possible weathered basalt or iron-rich slag

Basalt, tentatively; composition likely plagioclase and pyroxene with possible magnetite

Weathered iron-stained rock fragment

Uncertain from the image; likely an iron-oxide-stained, quartz- and feldspar-bearing rock

Small gray rock fragment

Undetermined; likely a common silicate-rich stone or concrete/road aggregate fragment

Weathered, rounded rock (likely metamorphic or igneous)

Undetermined; possibly a quartz- and feldspar-bearing rock

Rounded river pebble, likely weathered sandstone or volcanic rock

Indeterminate fine-grained lithic clast; possible sandstone (quartz-rich)

Gem-set gold ring

Likely gold alloy set with a colorless gemstone, possibly diamond or clear quartz; the stone cannot be identified reliably from the image

Weathered, quartz-rich rock (possibly quartzite)

Quartzite, composed predominantly of quartz (SiO₂); identification is uncertain from the photo

Goldstone (Red)

Aventurine Glass

Brick veneer, likely manufactured from clay-rich shale

Fired clay brick; chiefly aluminosilicate minerals, commonly mullite and glassy silicate phases after firing

Unidentifiable Rock Fragment

Faceted glass-like gemstone (likely synthetic quartz or cubic zirconia)

Identification uncertain; possibilities include synthetic quartz (SiO₂) or cubic zirconia (ZrO₂)

Possible flint or slag fragment

Microcrystalline quartz (chalcedony), or iron-rich industrial slag

Emerald and diamond ring

Emerald: beryl, Be3Al2Si6O18, colored green by chromium and/or vanadium; surrounding stones appear to be diamonds, crystalline carbon (C)

Iron-stained quartzite (likely)

Quartz-rich quartzite, predominantly SiO₂, with iron-oxide staining

Clear faceted gemstone, likely synthetic cubic zirconia

Cubic zirconia (zirconium dioxide, ZrO₂); visual identification is not definitive and diamond or synthetic moissanite are alternatives

Small weathered stone fragment

Undetermined; possibly a feldspar- or quartz-bearing rock fragment

Basalt Arrowhead (worked stone)

Aphanitic mafic volcanic rock (Basalt)

Smooth river pebble

Indeterminate lithology; likely fine-grained quartz-rich sandstone, siltstone, or weathered chert

Painted/tumbled stone specimens

Unidentified natural rock; likely a dark silicate stone and a weathered brown stone

Obsidian

Volcanic Glass (Silica-rich glass)

Amber-set ring

Amber (fossilized plant resin; organic mineraloid), set in a metal ring

Iridescent bismuth crystal

Bismuth (Bi), artificially crystallized and likely oxidized/coated

Small rough mineral/rock specimen (not confidently identifiable)

Undetermined; image detail is insufficient for a reliable identification

Goldstone (blue/black aventurine glass)

Man-made aventurine glass; silica glass containing metallic copper or other glittering inclusions

Likely bismuth crystal

Synthetic bismuth (Bi), crystallized from molten metal; not a natural rock-forming specimen

Polished black stone carving, likely soapstone/steatite

Steatite (massive talc), Mg₃Si₄O₁₀(OH)₂; exact material cannot be confirmed from the image

Unidentified dark, flat specimen

Indeterminate; image resolution is insufficient for mineral identification

Likely beach-worn glass and a pebble

The brown piece appears to be weathered glass (amorphous SiO₂-rich material); the pale piece is likely a small quartz-rich stone, possibly milky quartz.

Possible obsidian or slag glass

Volcanic glass, primarily SiO₂; alternatively industrial iron-rich glassy slag

Green sea glass (likely bottle glass)

Man-made soda-lime silicate glass; not a natural mineral

Colorless faceted gemstone (likely cubic zirconia)

Cubic zirconia, zirconium dioxide (ZrO₂); possibly synthetic quartz or glass imitation

Painted pebble, likely a smooth river stone

Unidentified fine-grained natural rock; exact lithology cannot be determined from the image

Bronze or iron-age decorated pottery sherd

Archaeological ceramic fragment; likely fired clay with impressed or molded decoration, not a natural rock

Concrete aggregate surface

Human-made cementitious composite; primarily calcium-silicate-hydrate cement with mixed silicate aggregate

Colorless faceted gemstone (most likely synthetic cubic zirconia)

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

Likely silicon carbide (carborundum)

Synthetic silicon carbide (SiC), likely blue-green crystalline grit