Limestone

Likely weathered limestone

Calcite-rich limestone (mostly CaCO₃), possibly dolomitic limestone

Weathered limestone fragment

Limestone, predominantly calcite (CaCO₃), possibly porous bioclastic limestone

Weathered limestone fragment

Calcite-rich limestone (CaCO₃), possibly chalky or fossiliferous limestone

Weathered limestone

Calcite-rich limestone (CaCO₃), possibly chalky micritic limestone

Lapis Lazuli and Amazonite

Complex silicate mineral aggregates (Lazurite, Calcite, Pyrite & Microcline feldspar)

Quartz-veined Limestone

Sedimentary limestone with quartz/calcite veinlets

Fossilized Coral (Honeycomb Coral)

Favosites (extinct genus of tabulate corals), CaCO3 (Calcium Carbonate)

Fossil coral (likely solitary rugose coral)

Rugosa; possibly genus Heliophyllum or similar

Chert (variations include Chalcedony and Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Bivalve Shell Fragment (Biogenic Calcite/Aragonite)

Calcium carbonate (CaCO3, primarily aragonite/calcite)

Fossiliferous Limestone or Mudstone

Sedimentary Rock with Invertebrate Fossils

Calcite on Limestone

Calcium Carbonate (CaCO3) on Sedimentary Rock

Lapis Lazuli

Lapis lazuli (complex rock; primarily Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Chert (with Quartz veins)

Microcrystalline Quartz (SiO2)

Fossilized coral or stromatoporoid

Calcareous fossil, likely colonial coral (phylum Cnidaria) or stromatoporoid sponge; commonly calcite/aragonite replaced by calcite

Weathered limestone pebble

Limestone, predominantly calcite (CaCO₃)

Rounded limestone pebble

Limestone, predominantly calcite (CaCO₃)

Marble

Metamorphosed Limestone / Calcite or Dolomite

Orange Calcite (Polished Point)

Calcium carbonate (CaCO3)

Flint or chert nodule

Microcrystalline quartz (SiO₂), commonly chalcedony with possible minor impurities

Fossilized Coral (Rugose Coral / Horn Coral)

Rugosa / Scleractinia

Fossiliferous limestone with a shell fossil

Bioclastic limestone containing a probable bivalve or brachiopod fossil; exact identification is not possible from the image alone.

Limestone with Calcite Veins

Sedimentary Calcium Carbonate (CaCO3)

Blue-gray limestone or marble fragment

Calcite-rich carbonate rock; likely calcitic marble (CaCO₃), though limestone is possible

Coral fossil (likely fossilized colonial coral)

Calcareous fossil coral; commonly *Scleractinia* or *Tabulate/ rugose coral* (identification requires close pore-pattern examination)

Sandstone / Limestone

Sedimentary Rock (Quartz Sandstone or Calcareous Grainstone)

Likely coral fragment or porous limestone

Calcareous biogenic carbonate, primarily calcite (CaCO₃); exact identification is uncertain from the image

Quartz on Limestone

Silicon Dioxide (SiO2) on Calcium Carbonate (CaCO3)

Limestone countertop or floor tile

Calcite-rich limestone, composed mainly of calcium carbonate (CaCO₃)

Chert Nodules in Limestone

Microcrystalline Quartz (SiO2) within Calcium Carbonate (CaCO3)

Tumbled fossiliferous limestone

Calcite-rich limestone (CaCO₃), possibly containing fossil fragments

Fossiliferous limestone, likely containing a large bivalve or gastropod fossil

Calcite-rich limestone (CaCO₃) with molluscan bioclast

Fossilized Shell Fragment

Invertebrate marine fossil, likely calcium carbonate replacement

Chert with Limestone

Silicon Dioxide (SiO2) in Calcium Carbonate (CaCO3) Matrix

Chert (Flint flake)

Microcrystalline Quartz (SiO2)

Galena

Lead Sulfide (PbS)

Nephrite Jade / Epidote Pebble

Ca2(Mg,Fe)5Si8O22(OH)2 / Ca2Al2Fe3+(SiO4)(Si2O7)O(OH)

Barite

Barium sulfate (BaSO4)

Chert

Chert (Microcrystalline Quartz)

Tiffany Stone

Fluorite-bearing Opalized Breccia

Brachiopod Fossil

Rhynchonellida (Order)

Chert (specifically Tan/Brown Chert)

Chert (SiO2)