Mineraloid (Man Made)

Iron-rich concretion or weathered ironstone nodule

Goethite–hematite-rich limonite concretion (tentative)

Swirled Agate Bead

Silicon Dioxide (SiO2)

Tumbled obsidian

Volcanic glass; chiefly SiO₂, noncrystalline

Concrete-like aggregate surface with embedded rock fragments

Anthropogenic concrete or exposed aggregate; not a natural rock specimen

Red gemstone ring, likely garnet or synthetic ruby

Possibly almandine garnet (Fe₃Al₂(SiO₄)₃) or corundum/ruby (Al₂O₃); image alone cannot distinguish

Tumbled greenstone (likely serpentinite or green jasper)

Serpentinite, commonly dominated by serpentine-group minerals (Mg₃Si₂O₅(OH)₄); exact identification requires testing

Quartz (Microcrystalline/Chert)

Silicon Dioxide (SiO2)

Turquoise

Hydrated phosphate of copper and aluminium [CuAl6(PO4)4(OH)8·4H2O]

Chert (Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Carved serpentine pendant

Serpentine-group minerals, commonly antigorite/lizardite (Mg₃Si₂O₅(OH)₄), possibly mixed with chlorite or other inclusions

Slag (Industrial Glass Slag)

Amorphous Silica / Ferro-silicate Slag

Flint

Silicon Dioxide (SiO2) - Chert variety

Coquina / Fossiliferous Limestone

Fossiliferous Limestone (Calcite, CaCO3)

Granodiorite with Quartz Veining

Granodiorite (containing Plagioclase Feldspar, Quartz, and Biotite/Hornblende) with Quartz (SiO2) veins

Chert (variations include Flint/Novaculite)

Chert (formula: SiO2)

Chert (often called Flint for darker varieties)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Polished serpentine pendulum

Serpentine-group minerals, chiefly antigorite/lizardite; approximate formula Mg₃Si₂O₅(OH)₄

Granite

Phaneritic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Limestone

Calcium Carbonate (CaCO3)

Diamond ring

Diamond, crystalline carbon (C)

Diamond

Carbon (C)

Likely bituminous coal

Coal, predominantly carbon-rich organic matter; exact rank cannot be confirmed from the image

Pyrite

Iron Disulfide (FeS2)

Rough Diamond

Diamond (Pure Carbon: C)

Polished dendritic agate cabochon (likely agate or jasper)

Microcrystalline quartz, SiO₂, commonly chalcedony with iron-oxide inclusions

Blue-green gemstone ring, likely treated turquoise or synthetic/treated beryl

Indeterminate from image; possibilities include turquoise (CuAl6(PO4)4(OH)8·4H2O), apatite, or treated beryl

Quartzite

Quartzite (SiO2)

Lapis lazuli and green-blue chalcedony jewelry

Lapis lazuli: lazurite-bearing metamorphic rock, chiefly lazurite (Na₃Ca(Al₃Si₃O₁₂)S) with calcite and pyrite; second stone: likely chrysoprase or green-blue chalcedony (microcrystalline quartz, SiO₂)

Faceted gemstone in a jewelry setting

Indeterminate from image; likely quartz, cubic zirconia, or another transparent faceted stone

Weathered vesicular volcanic rock, likely pumice or scoria

Vesicular rhyolitic pumice or basaltic scoria; exact identification requires a clearer image and tests

Vesicular volcanic rock, likely weathered pumice or scoria

Pumice/scoria; predominantly volcanic glass and feldspar, with possible iron oxides

Diamond

Carbon (C)

Pink calcite (likely)

Calcite — calcium carbonate, CaCO₃

Polished red jasper beads

Jasper, microcrystalline quartz (SiO₂) colored mainly by iron oxides

Diamond

Carbon (C)

Loose faceted colorless gemstones, likely quartz or glass-like mineral chips

Most consistent with quartz (SiO₂), though the photograph cannot exclude synthetic cubic zirconia or glass

Diamond

Diamond (pure Carbon, C)

Pyrite (Fool's Gold)

Iron Disulfide (FeS2)

Polished jasper pendant

Jasper, microcrystalline quartz (SiO₂) with iron-oxide and other mineral inclusions

Chrysoprase- or serpentine-bearing quartz vein with pyrite

Quartz (SiO₂) with iron sulfide, chiefly pyrite (FeS₂), in altered Mg-rich rock; green material may be serpentine or nickel-bearing chalcedony

Brown agate or chalcedony cabochon pendant

Microcrystalline quartz (SiO₂), likely brown chalcedony/agate

Slag (Industrial Glass)

Artificial Vitreous Silicate