Organic (Anthropogenic)

Chert / Chalcedony

Silicon Dioxide (SiO2)

Chert / Flint

Microcrystalline Quartz (SiO2)

Chert (Nodule)

Cryptocrystalline Quartz (SiO2)

Pyrite

Iron Disulfide (FeS2)

Flint

Chert (Silicon dioxide, SiO2)

Chert Nodules in Limestone

Microcrystalline Quartz (SiO2) within Calcium Carbonate (CaCO3)

Chert (variously known as Flint)

Silicon Dioxide (SiO2)

Shungite

Non-crystalline carbonoid (Shungite)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chert (Flint)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Pyrite in Shale

Iron Disulfide (FeS2)

Chert (Arrowhead variety)

Chert (SiO2)

Chert Nodule (Flint)

Cryptocrystalline quartz (SiO2)

Mother of Pearl and Onyx

Aragonite (Mother of Pearl) and Chalcedony (Onyx)

Chert (Flint)

Silicon Dioxide (SiO2)

Chert (Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert

Microcrystalline Quartz (SiO2)

Chert (Jasper)

Cryptocrystalline Quartz (SiO2)

Red Chert

Microcrystalline Quartz (SiO2)

Chert (Flint/Jasper)

Silicon Dioxide (SiO2)

Chert (Jasper/Flint variety)

Silicon Dioxide (SiO2)

Chert (Jasper variety)

Microcrystalline Quartz (SiO2)

Petrified wood

Silicified fossil wood, primarily quartz (SiO₂) replacing cellulose

Fossil gastropod shell

Fossilized marine gastropod; exact genus/species cannot be determined from the image

Mocha Stone (Dendritic Agate)

Silicon Dioxide (SiO2) with Manganese/Iron inclusions

Fossiliferous Sandstone / Mudstone

Sedimentary Rock (Clastic with Fossiliferous Inclusions)

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Moss-covered Limestone with Quartz/Calcite Pocket

Calcium Carbonate (CaCO3) rock with biological moss coating

Glauconite

Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2

Likely coal (possibly anthracite)

Coal, composed chiefly of carbon-rich organic matter; rank cannot be confirmed from the photograph

Tumbled brown chert (likely flint)

Microcrystalline quartz/chalcedony, SiO₂

Fossiliferous limestone

Bioclastic carbonate rock; predominantly calcite (CaCO₃)

Fossilized bone fragment

Petrified vertebrate bone; mineralized hydroxyapatite replaced or infilled by silica/carbonates

Polished amber (likely copal or amber)

Fossilized tree resin; amber is predominantly polymerized diterpenoid resin, while copal is younger, incompletely polymerized resin

Septarian nodule (likely polished)

Calcite- and/or aragonite-filled mudstone concretion; commonly Fe-bearing claystone/mudstone matrix

Ironstone Concretion (Boxwork)

Siderite-Limonite Concretion (FeO(OH)·nH2O)

Chert Nodule

Microcrystalline Quartz (SiO2)

Unidentified Dark Mineral or Rock

Indeterminate (Likely Silicon Dioxide or Carbon-based)

Polished green moss agate cabochon

Moss agate: microcrystalline quartz (SiO₂) with included chlorite/actinolite or iron-manganese minerals

Amber

Fossilized Tree Resin

Fluorite

Fluorite (CaF2)

Amber

Fossilized tree resin