Mineraloid (Man Made)

Quartzite

Metamorphic Quartz Rock (SiO2)

Yellow chalcedony (possibly iron-stained agate)

Microcrystalline quartz, SiO₂

Orange glassy slag (industrial by-product)

Iron-rich silicate glass; composition varies, commonly Fe–Ca–Al silicate

Chalk

Micrite (primarily Calcium Carbonate or CaCO3)

Sandstone (Quartzose)

Sandstone (SiO2 dominated)

Pearl

Organic gemstone (Calcium carbonate - CaCO3)

Chert (variations include Flint)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Coal (Bituminous Coal)

Caustobiolith / Sedimentary Rock

Sandstone

Arenite (SiO2 composition dominant)

Polished/tumbled brown-and-white mineral fragment

Indeterminate; possibly quartz-rich jasper, brecciated jasper, or an iron-stained quartz mineral

Tumbled quartz-rich pebble

Microcrystalline quartz (SiO₂), possibly milky quartz or quartzite

Blue-green chrysocolla rough specimen

Chrysocolla, hydrated copper aluminosilicate; commonly associated with malachite, quartz, and limonite

Diamond

Native Carbon (C)

Quartzite

Metamorphic Quartzite (SiO2)

Yellow chalcedony (likely dyed or heat-treated)

Microcrystalline quartz, SiO₂ (chalcedony)

Diamond

Carbon (C)

Diamond

Carbon (C)

Diamond

Carbon (C)

Multicolor quartz bead bracelet

Quartz (silicon dioxide, SiO₂); bead colors may be from different varieties or treated quartz

Sandstone

Arenite (composed primarily of SiO2)

Tumbled greenstone (probable serpentinite)

Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), possibly with chlorite, magnetite, or talc

Tumbled green-brown stone, likely serpentine

Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), commonly with magnetite

Tiny rounded brown mineral grain

Indeterminate; possibly iron oxide, garnet, or a weathered sulfide grain

Sandstone

Clastic Sedimentary Rock

Pearl (nacre)

Calcium Carbonate (mostly CaCO3 as Aragonite) and Conchiolin

Quartzite

Metamorphic Quartzite (SiO2)

Sandstone (Quartzose)

Arenite (primarily SiO2)

Limonite and Goethite (Ironstone)

Hydrous Iron Oxide Mixture (FeO(OH)·nH2O)

Red jasper

Jasper, an opaque microcrystalline variety of quartz (SiO₂), colored chiefly by iron oxides

Milky quartz

Quartz (silicon dioxide, SiO₂)

Sandstone

Arenite (SiO2, often with CaCO3 or Fe2O3 cement)

Quartzite

Metamorphic Quartzite (SiO2)

Quartzite

Metamorphic Quartzite (SiO2)

Quartzite

Metamorphic Quartzite (primarily SiO2)

Quartzite

Metamorphic Quartzite (primarily SiO2)

Sandstone

Arenite

Diamond

Diamond (pure carbon C)

Tumbled quartz (likely milky quartz)

Quartz, silicon dioxide (SiO₂)

Tumbled chalcedony pendant (likely agate)

Chalcedony, microcrystalline quartz (SiO₂); the pale bands suggest agate

Quartzite

Metamorphic Quartz Rock (SiO2)

Red Quartzite

Quartzite (Metamorphosed Quartz Arenite)

Fossil oyster shell

Oyster (family Ostreidae), preserved as fossilized calcite/aragonite shell