Sedimentary (Biogenic Sediment Or Biological Remain)

Banded chert or siliceous mudstone

Microcrystalline quartz (chalcedony), SiO₂; possibly ferruginous shale

Chert or flint (weathered brown variety)

Microcrystalline quartz, SiO₂ (chalcedonic quartz)

Chert (Flint / Chalcedony pebble)

Silicon Dioxide (SiO2)

Chert or flint with chalcedony/quartz veins

Microcrystalline silica: primarily quartz (SiO₂), including chalcedony; possible fossiliferous limestone or silicified material

Water and Silt (Sedimentary Environment)

Suspended Sediment / H2O (dihydrogen monoxide)

Ironstone Nodules (Iron Concretion)

Siderite or Hematite Concretion

Chert

Microcrystalline Quartz (SiO2)

Sea Shell (Fighting Conch Fragment)

Calcium Carbonate (CaCO3) - Strombus alatus fragment

Stromatolite

Biogenic Sedimentary Rock (Precambrian Stromatolite fossil)

Iron-stained chert or siliceous mudstone

Microcrystalline quartz (SiO₂), likely chert with hematite/goethite staining

Polished fossil shell or bone fragment (tentative)

Indeterminate biogenic carbonate or fossilized bone; possibly a small gastropod/bivalve fragment

Fossil Coral

Cnidaria fossil (often Calcium Carbonate / CaCO3)

Granitic Sand

Detrital sediment (predominantly Quartz, Feldspar, and Mica)

Chert / Fossilized Burrow Cast

Microcrystalline Quartz (SiO2) with Trace Carbonates

Chert / Flint

Microcrystalline Quartz (SiO2)

Petrified Wood

Silicified Wood (primarily SiO2)

Banded chert or flint

Microcrystalline quartz (SiO₂), likely with iron-oxide and dark organic/mineral impurities

Limestone (Flagstone)

Fossiliferous Limestone (CaCO3)

Fossilized tooth or jaw fragment (likely fish or reptile)

Indeterminate vertebrate bone/tooth; mineralized hydroxyapatite, commonly Ca₅(PO₄)₃(OH)

Fossiliferous Limestone (Shell Fragment)

Biogenic Limestone (Calcium Carbonate / CaCO3)

Fossiliferous limestone pebble

Calcite-rich limestone (primarily CaCO₃), with possible fossil or fossil-fragment patterns

Fossil-bearing sedimentary rock (possible bone or shell fossil)

Unidentified fossiliferous sedimentary matrix; exact fossil and host rock cannot be determined from the image

Fossilized Brachiopod Shell in Matrix

Phylum Brachiopoda (typically Calcium Carbonate or Chitinophosphatic)

Native gold (gold nugget)

Native gold, Au; commonly alloyed with silver and copper (electrum when silver-rich)

Flint or chert fragment

Microcrystalline quartz (SiO₂), typically chalcedony with possible impurities

Fossilized shell or bone fragment

Likely bioclast composed mainly of calcium carbonate (calcite/aragonite); exact organism is indeterminate from the image

Flint or chert

Microcrystalline quartz (SiO₂), likely gray chert/flint

Chert or flint fragment

Microcrystalline quartz (SiO₂), possibly iron-stained chert

Chalky limestone

Micritic limestone, predominantly calcite (CaCO₃)

Gastropod Steinkern (Internal Mold Fossil)

Gastropoda (Class); Internal mold or 'Steinkern' composed of Calcium Carbonate (CaCO3) or Sedimentary matrix

Yellow-brown chert or silicified rock fragment

Microcrystalline quartz (SiO₂), likely chert or chalcedony-rich material

Weathered chert or flint pebble

Microcrystalline quartz (SiO₂), likely chert/flint with possible carbonate or quartz vein

Pyrite

Iron Sulfide (FeS2)

Weathered chert or chalcedony pebble

Microcrystalline quartz (SiO₂), likely chert/chalcedony

Fossiliferous Sedimentary Rock

Sedimentary Rock with Invertebrate Fossil Imprint

Fossil tooth fragment

Likely fossilized shark tooth or marine vertebrate tooth; exact taxon cannot be determined from the image

Pearl (in Marcasite Jewelry)

Biogenic Calcium Carbonate (primarily Aragonite, CaCO3)

Jasper containing fossilized inclusions

Silicon Dioxide (SiO2) with trace impurities and biogenic inclusions

Iron-rich chert or weathered ironstone

Microcrystalline quartz (SiO₂) with iron oxides/hydroxides, possibly hematite/goethite

Brown flint or chert pebble

Microcrystalline quartz (SiO₂), commonly with iron-oxide staining

Tumbled brown chert (likely flint)

Microcrystalline quartz/chalcedony, SiO₂

Banded Chert

Microcrystalline Quartz (SiO2)