Organic Gemstone (Not A Rock)

Chert (Brecciated or Veined)

Silicon Dioxide (SiO2)

Chert with Quartz Veining

Silicon Dioxide (SiO2)

Chert (varieties include Flint and Jasper)

Silicon Dioxide (SiO2) / Microcrystalline Quartz

Moonstone

Orthoclase Feldspar (KAlSi3O8)

Fossilized Coral

Scleractinia (fossil order), primarily Calcium Carbonate (CaCO3)

Yellow Jasper / Chert

Jasper (Silica/Quartz) - SiO2

Petrified Wood

Silicified Wood (SiO2)

Chert (Jasper/Jasperoid)

Chert (chemically precipitated microcrystalline Quartz, SiO2)

Chert (specifically Tan Chert or Flint)

Silicon Dioxide (SiO2)

Red Chert (Jasper)

Cryptocrystalline Quartz (SiO2) with iron oxide inclusions

Chert (specifically Flint or Jasper variant)

Microcrystalline silica (SiO2)

Petrified Wood

Silicified Wood (primarily Chalcedony or Quartz, SiO2)

Chert (and/or River Pebble)

Microcrystalline silica (SiO2)

Yellow Jasper (Iron-stained Chert)

Silicon Dioxide (SiO2) with iron oxide (Limonite/Goethite) inclusions

Moss Agate

Chalcedony (SiO2) with inclusions of hornblende or chlorite

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2 with iron inclusions)

Amethyst

Amethyst (Silicon Dioxide, SiO2 with Iron impurities)

Coal (Bituminous or Anthracite)

Carbonaceous sedimentary rock (primarily Carbon, C)

Fossiliferous Limestone

Biogenic Limestone (Calcium Carbonate, CaCO3)

Chert (Flint)

Chert (Silicon Dioxide, SiO2)

Red Jasper

Jasper (Silicon Dioxide, SiO2)

Banded Chert (River Siltstone)

Microcrystalline Quartz (SiO2)

Crinoid Fossil in Limestone

Crinoid (Class Crinoidea) in Fossiliferous Limestone (CaCO3)

Chert (Nodular Chert)

Silicon Dioxide (SiO2)

Chert (and/or Siltstone River Pebble)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Moss Agate

Chalcedony (Silicon Dioxide) with dendritic inclusions (SiO2)

Chert (Jasper/Flint variety)

Microcrystalline quartz (SiO2)

Chert / Pink Flint

Cryptocrystalline Quartz (SiO2)

Chert (with Liesegang Banding)

Microcrystalline quartz (SiO2)

Sandstone (likely Fossilized Wood or Concrete Simulacrum)

Arenite / Silicified Wood / Anthropogenic Concrete

Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

Chert (Field Stone)

Microcrystalline / Cryptocrystalline Quartz (SiO2)

Unakite

Epidotized Granite

Carnelian (Orange Chalcedony)

Silicon Dioxide (SiO2)

Jasper

Jasper (Silicon Dioxide) - SiO2

Turquoise, Pearl, and Coral Necklace

CuAl6(PO4)4(OH)8·4H2O (Turquoise) / CaCO3 (Pearl and Coral)

Olivine in Basalt (Peridot)

Magnesium Iron Silicate (Mg,Fe)2SiO4 (Mineral) within Basalt (Rock)

Chert (often called Jasper or River Siltstone)

Microcrystalline Quartz (SiO2)

Petrified Wood

Silicified Wood (primarily SiO2 - Silicon Dioxide)

Anthracite Coal

Anthracite (Carbon-rich metamorphic coal)