Not A Natural Rock

Unidentified natural rock specimens

Likely weathered, feldspar-rich granite or granitic pegmatite; exact identification requires close examination or testing

Man-made Slag (Industrial Byproduct)

Anthropogenic Glassy Residue

Concrete / Anthropogenic Conglomerate

Man-made composite material (Portland cement, aggregate, and water)

Smoky quartz and clear/white quartz bead necklace

Quartz, silicon dioxide (SiO₂); smoky variety colored by irradiation-related defects

Gold ring with a clear faceted gemstone

Likely diamond (carbon, C); the photograph is insufficient to confirm the stone or metal

Diamond-encrusted microphone-shaped pendant

Diamond (natural or synthetic) set in gold-colored metal; exact stones and metal cannot be confirmed visually

Weathered concrete or cementitious slab (not natural rock)

Artificial calcium-silicate cement composite; likely Portland cement concrete

Weathered biotite granite or granitic gneiss

Felsic granitoid, chiefly quartz, K-feldspar, plagioclase, and biotite; possible gneissic deformation

Bowling Ball (Brunswick T-Zone Deep Space)

Polyester resin / Polyurethane polymer

Gravel (mixed crushed stone)

Unidentified aggregate of crushed natural rock fragments

Baked-clay ceramic fragment (likely brick or pottery)

Fired clay, primarily aluminosilicate minerals; not a natural rock

Concrete-like aggregate surface with embedded rock fragments

Anthropogenic concrete or exposed aggregate; not a natural rock specimen

Green glass-like cabochon, likely synthetic glass or resin

Unidentified green transparent material; possibly molded glass, synthetic spinel, or resin

Garnet ring

Likely almandine or pyrope garnet, an Fe–Mg–Al silicate in the garnet group; exact identity cannot be confirmed visually

Fossil fish impression/cast (likely small ray-finned fish)

Unidentified Actinopterygii; possibly a fish fossil in laminated shale

Small rock fragment (unidentified)

Undetermined; the image does not show enough detail for reliable identification

Exposed aggregate concrete (stone-chip surface)

Portland-cement concrete containing natural aggregate; not a natural rock

Weathered granite fragment

Granite, chiefly quartz (SiO₂), feldspar, and mica

Faceted colorless gemstone, likely cubic zirconia or diamond

Cubic zirconia (zirconium dioxide, ZrO₂) or diamond (carbon, C)

Green-and-white terrazzo (likely serpentine/marble aggregate)

Composite decorative stone; probable serpentinite (Mg₃Si₂O₅(OH)₄) with white calcite marble fragments in cementitious matrix

Unidentified gray stone/concrete-like fragment

Indeterminate; likely a fine-grained carbonate or cementitious geological fragment

Dark gray rock fragment (unidentified)

Undetermined; the image does not show enough detail for reliable identification

Green stone fragment (unidentified)

Undetermined; possibly serpentine or greenstone, but the image is insufficient for identification

Multi-stone gemstone ring

Likely faceted blue topaz or synthetic blue stone with clear stones, possibly cubic zirconia or diamond; metal setting appears silver-colored alloy

Red Painted Rock

Artificial Coated Lithic Fragment

Smooth river pebble (exact rock type indeterminate)

Unidentified rounded lithic clast; composition cannot be determined from the photograph

Unidentified small rock fragment

Undetermined; the photo does not show enough detail for reliable mineral identification.

Angular gray rock fragments

Unidentified fine-grained rock; the image does not show diagnostic features sufficient for a specific identification

Green aventurine cabochon earrings

Aventurine quartz (SiO₂), likely green quartzite with fuchsite mica

Clear gemstone earring (likely cubic zirconia)

Cubic zirconia (synthetic zirconium dioxide, ZrO₂); identification from the image is uncertain

Smooth gray pebbles

Unidentified rounded rock fragments; composition cannot be determined from the image

Parian marble sculpture fragment

Marble, predominantly calcite (CaCO₃), likely a fine-grained Greek island marble

Unidentified gray rock fragment

Indeterminate from image; possibly quartz- or feldspar-rich silicate material

Blue opalite glass cabochon (likely imitation opal)

Man-made opalescent glass; not a natural mineral

Gold coin pendant on a chain

Gold (Au), likely a coin set in a gold-colored metal mount

Blue glass-like bead or gemstone keychain ornament

Indeterminate; likely cobalt-blue glass or synthetic blue spinel, not identifiable as a natural mineral from the image

Gray rock (possibly basalt or fine-grained granite)

Undetermined; no diagnostic minerals are visible

Opalite-style glass pendant

Man-made opalescent glass (not natural opal)

Concrete or asphalt-like aggregate surface with a dark fragment

Uncertain; likely artificial concrete containing mixed lithic aggregate, not a natural rock

Quartz-rich pegmatite with drusy quartz

Quartz (SiO₂) in a granitic pegmatite, likely with feldspar and mica inclusions

Quartz pebble in concrete

Quartz (SiO₂), embedded in Portland-cement concrete

Carnelian (red-orange chalcedony) beads

Microcrystalline quartz, SiO₂; chalcedony colored chiefly by iron oxides