Organic Gemstone (Not A Rock Or Mineral In The Traditional Sense, But Bio Mineralized Material)

Chert (likely chalcedony-rich flint)

Microcrystalline quartz, SiO₂ (quartz/chalcedony)

Tumbled black-and-white stone, likely dalmatian jasper

Quartz-rich porphyritic rhyolite (commercially called dalmatian jasper), with black aegirine/arfvedsonite-like inclusions

Chert Nodule

Microcrystalline Silica (SiO2)

Fossilized Coral (Petrified Coral)

Lithostrotionella (example genus) / Scleractinia

Yellow Ochre / Limonite

Limonite (FeO(OH)·nH2O)

Fossil scallop shell

Bivalve mollusk shell, likely family Pectinidae; primarily calcite (CaCO₃)

Quartz (Milky/Clear Quartz)

Silicon Dioxide (SiO2)

Quartz (Rose or Clear variety)

Silicon Dioxide (SiO2)

Fossilized Bone

Petrified Bone / Biogenic Sedimentary

Mammoth Tooth

Mammuthus primigenius (Tooth fragment)

Likely bituminous coal

Coal, predominantly carbon-rich organic matter with variable maceral and mineral content

Tumbled brown agate (likely moss or plume agate)

Microcrystalline quartz, chiefly chalcedony (SiO₂), with iron-oxide and possibly mineral inclusions

Amethyst (rough chip)

Quartz, purple variety; silicon dioxide (SiO₂)

Amethyst (likely tumbled or cut fragment)

Quartz, silicon dioxide (SiO₂), purple variety colored mainly by iron impurities and irradiation

Quartz

Silicon Dioxide (SiO2)

Brecciated quartz vein rock

Quartz (SiO₂), with iron-oxide staining and likely feldspar/carbonate gangue

Petrified Wood

Silicified Wood (Silicon Dioxide - SiO2)

Weathered greenish mafic rock fragment

Likely altered basalt or basaltic-andesite; exact identification is uncertain from the photograph

Yellow Sapphire or Citrine

Al2O3 (Corundum) or SiO2 (Quartz)

Fossil gastropod shell

Fossilized marine gastropod; exact genus/species requires locality and examination

Baroque Pearl

Biogenic Calcium Carbonate (Aragonite/Conchiolin)

Quartz (Cut and Polished Sphere)

Silicon Dioxide (SiO2)

Dark mineral nodule with white veining

Possibly a calcite-veined manganese- or iron-rich concretion; exact identification requires testing

Pearl

Calcium Carbonate (Aragonite and Calcite), CaCO3

Pearl

Calcium Carbonate (CaCO3) in the form of Aragonite

Weathered iron-rich rock fragment

Likely limonite/goethite-bearing rock, possibly altered pyrite or mica schist

Shark Tooth Fossil

Vertebrate fossilized tooth

Amber

Fossilized plant resin; chiefly an organic polymer (succinite), not a crystalline mineral

White Quartz

Silicon Dioxide (SiO2)

Fossilized Bone Fragment

Vertebrate Fossil

Dendritic Agate

Silicon Dioxide with Manganese/Iron oxide inclusions (SiO2)

Weathered quartz-rich rock or fossil fragment

Indeterminate; likely quartz-bearing sandstone or siliceous fossil material

Tumbled amethyst

Quartz, SiO₂; purple variety colored mainly by iron-related defects and irradiation

Fossilized bivalve shell or shell-rich limestone

Likely an indeterminate fossil mollusk; calcite/aragonite (CaCO₃), possibly preserved in limestone

Likely slate

Slate, a fine-grained metamorphic rock composed mainly of mica-group minerals and quartz

Fossilized bone fragment

Fossil bone, composed chiefly of carbonate-fluorapatite (bioapatite)

Pyrite-rich sulfide ore (likely pyrite with chalcopyrite)

Pyrite, FeS₂; possible chalcopyrite, CuFeS₂, and minor quartz or sphalerite

Turquoise

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

Sandstone (Whetstone/Sharpening Stone)

Siliciclastic Sandstone (SiO2 dominant)

Clear Quartz

Silicon dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Amber (Copal)

Organic gemstone, fossilized tree resin (often immature amber or copal)