Organic Structure (Not A Rock)

Petrified Wood

Silicified Wood (primarily SiO2 - Silicon Dioxide)

Chert (often called Jasper or River Siltstone)

Microcrystalline Quartz (SiO2)

Anthracite Coal

Anthracite (Carbon-based metamorphic rock, 86-97% C)

Quartz (Druzy) in host rock

SiO₂ (Silicon Dioxide) as Quartz, with unspecified host rock components (likely silicates and iron oxides)

Chert with Quartz/Calcite Vein

Microcrystalline Silica (SiO2)

Chert (with Quartz vein)

Chert (Silicon Dioxide, SiO2)

Chert (Iron-stained)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Shungite

Non-crystalline carbon (high-carbon metamorphic rock)

Red Chert (Jasper)

Chert / Microcrystalline Quartz (SiO2)

Moss Agate

Agate (Silicon Dioxide, SiO2) with dendritic inclusions

Shale or Mudstone (Based on appearance)

Shale (fine-grained, laminated fissile sedimentary rock) / Mudstone (fine-grained, non-fissile sedimentary rock)

Amber (Rough Baltics/Beach Specimen)

Succinicum (Organic Gemstone - Fossilized Resin)

Pyrite in Shale

Iron Sulfide (FeS2) in Argillaceous Shale

Petrified Wood

Silicified Wood (primarily SiO2 - Silicon Dioxide)

Chert (containing Flint and Calcareous inclusions)

Silicon Dioxide (SiO2) with Calcium Carbonate (CaCO3) impurities

Chert (Yellow Jasper/Flint)

Silicon Dioxide (SiO2)

Chert (Pebble)

Microcrystalline silica (SiO2)

Amber

Succinite (with empirical formula approximately C10H16O)

Banded Chert (with Quartz Vein)

Microcrystalline Silica (SiO2)

Chert (Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Cherty Flint/Jasper variety)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Moss Agate

Silicon Dioxide (SiO2) with inclusions of Manganese or Iron oxide

Not a rock, mineral, or geological specimen

Chert (Iron-stained)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert / Jasper

Microcrystalline Quartz (SiO2)

Chert (Jasper/Ironstone variety)

Silicon Dioxide (SiO2) with iron oxide inclusions

River Stone (Chert/Siltstone)

Cryptocrystalline Quartz (SiO2) with trace impurities

Chert (and Limestone) River Cobble

Microcrystalline Quartz (SiO2) within Calcium Carbonate (CaCO3)

Shale

Fissile mudstone (primarily clay minerals and silt-sized quartz)

Chert (Yellow/Tan)

Microcrystalline Quartz (SiO2)

Stromatolite

Biogenic Sedimentary Rock (composed predominantly of CaCO3)

Pyrite in Shale

Iron Disulfide (FeS2) in Argillaceous Shale

Chert (specifically Flint or Gray Chalcedony)

Microcrystalline Quartz (SiO2)

Pink Opal

Amorphous Hydrous Silica (SiO2·nH2O)

Chert (Nodule)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Sandstone Concretion

Clastic sedimentary rock (primarily Quartz SiO2)

Chert (Iron-stained)

Chert (Silicon Dioxide, SiO2)

Fossiliferous Limestone

Calcite-rich Sedimentary Rock (CaCO3)

Chert (River Pebble)

Microcrystalline Quartz (SiO2)

Chert (Iron-Stained)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Chert (Brecciated River Cobble)

Silicon Dioxide (SiO2)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)