Industrial Byproduct (Anthropogenic Material)

Limestone Pebble

Sedimentary Calcium Carbonate (CaCO3)

Sandstone (Ferruginous)

Arenite with Iron-Oxide Cement (primarily SiO2 with Fe2O3/FeOOH)

Coal (Anthracite/Bituminous)

Carbo fossilium (primarily Carbon)

Red Sandstone

Arenite (with Iron Oxide / Hematite), Formula: SiO2 (Quartz) + Fe2O3 (Hematite coating)

Grey Quartzite Pebble

Quartzite (primarily SiO2)

Blue Lepidolite

Lepidolite (K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2)

Quartzite

Quartzite (primarily SiO2)

Diamond

Carbon (C)

Greywacke

Lithic Sandstone (Greywacke)

Diamond (in Jewelry)

Diamond (Carbon, C)

Agate (Chalcedony)

Silicon Dioxide (SiO2)

Diamond

Carbon (C)

Chondrite Meteorite

Stony Meteorite (Ordinary Chondrite)

Hag Stone

Flint / Chert / Limestone concretion with a natural hole

Possible iron-rich concretion or weathered ironstone

Goethite/limonite-rich ironstone; exact identification requires testing

Iron-rich vesicular rock, possibly slag or basalt

Uncertain; likely basaltic rock (plagioclase–pyroxene–iron oxide) or industrial iron slag

Polished brown jasper

Jasper, microcrystalline quartz (SiO₂) with iron-oxide impurities

Orbicular rhyolite (likely)

Rhyolite, a silica-rich volcanic rock; commonly quartz, alkali feldspar, plagioclase, and iron-rich alteration minerals

Unidentified dark pebble

Undetermined; possibly polished basalt, chert, or iron-rich stone

Sea Glass

Amorphous Silica (SiO2) with various additives

Rough Blue Diamond

Carbon (C)

Diamond (in jewelry setting)

Adamantine Carbon (C)

Diamond (Emerald Cut)

Carbon (C)

Yellow Diamond (Faceted)

Diamond (pure carbon) with nitrogen impurities, C

Quartzite Pebble

Quartzite (SiO2 with minor impurities)

Diamond

Carbon (C)

Diamond

Carbon (C)

Diamond

Natural Diamond (Carbon, C)

Weathered quartz-rich rock, possibly quartzite or quartz vein material

Quartz (SiO₂), likely with feldspar, mica, and iron-oxide staining

Gray Limestone

Calcium Carbonate (CaCO3)

Diamond

Native Carbon (C)

Dyed Chalcedony (Agate)

Silicon Dioxide (SiO2) with artificial pigment

Diamond

Carbon (C)

Pumice (specifically a water-worn, weathered variety)

Vesicular volcanic glass

Cubic Zirconia (Diamond Simulant)

Zirconium Dioxide (ZrO2)

Gypsum (Wallboard/Drywall)

Calcium Sulfate Dihydrate (CaSO4·2H2O)

Weathered quartz-rich stone, possibly fossiliferous limestone

Indeterminate; likely calcite-rich limestone (CaCO₃) or weathered quartz-bearing rock

Quartz (Engineered Stone Countertop)

Silicon Dioxide (SiO2) with polymer resins

Polished/tumbled brown jasper or iron-rich chert

Microcrystalline quartz (SiO₂), commonly colored by hematite/goethite

Polished dark chert or flint

Microcrystalline quartz (SiO₂), commonly called chert; possibly flint

Yellow chalcedony (likely lemon quartz or citrine)

Cryptocrystalline silica, SiO₂; possible quartz variety

Tumbled brown stone, likely jasper or iron-stained quartz

Microcrystalline quartz (SiO₂), possibly chalcedony/jasper with iron-oxide inclusions