Organic Gemstone (Often Associated With Sedimentary Sequences)

Carnelian

Carnelian (SiO2)

Chert (specifically Banded Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Coquina

Biogenic Limestone (Calcium Carbonate - CaCO3)

Chert (including Flint and Jasper variants)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (includes Flint & Jasper)

Chert (Siliceous sedimentary rock, chemical formula SiO2)

Chert (Septarian or Nodular variety)

Microcrystalline Quartz (SiO2)

Chert (Nodule)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Fluorite

Fluorite (Calcium Fluoride, CaF2)

Petrified Wood

Silicified Wood (SiO2)

Fossilized Crinoid Stem Segment

Crinoid (Phylum Echinodermata, Class Crinoidea)

Tufa

Calcareous Tufa (Calcium Carbonate, CaCO3)

Carnelian

Silicon Dioxide (SiO2) - variety of Chalcedony

Quartz (beads)

SiO2 (Silicon Dioxide)

Chert (Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Emerald

Beryl (Be₃Al₂Si₆O₁₈), specifically the green variety colored by trace amounts of chromium or vanadium.

Chert (and/or River Pebble)

Microcrystalline quartz (SiO2)

Quartz Geode in Chert/Limestone Matrix

Silicon Dioxide (SiO2) within Sedimentary Host Rock

Chert (Flint)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Pink Opal (Common Opal)

Amorphous Hydrated Silica (SiO2·nH2O)

Charoite

(K,Sr,Ba,Ca)15-16(Na,Ca)8(Si,Al)24O60(OH,F)4 · nH2O (Hydrated silicate of potassium, calcium, and sodium)

Chert (Flint variety)

Microcrystalline context of Quartz (SiO2)

Green Aventurine

Aventurine (a variety of Quartz, SiO2 with fuchsite inclusions)

Peach Moonstone

Orthoclase Feldspar (KAlSi3O8) with inclusions

Limonite-stained Chert

Silicon Dioxide (SiO2) with Hydrated Iron Oxide (FeO(OH)·nH2O)

Chert / River Jasper

Microcrystalline Quartz (SiO2)

Chert (Nodule)

Silicon Dioxide (SiO2)

Chert (containing Fossil Inclusions)

Microcrystalline Quartz (SiO2)

Green Fluorite

Calcium Fluoride (CaF2)

Fluorite

Calcium Fluoride (CaF2)

Moonstone (bead form)

Potassium Aluminum Silicate (KAlSi3O8) - a variety of Orthoclase Feldspar

Fuchsite

Chromium-rich Muscovite (K(Al,Cr)2(AlSi3O10)(OH)2)

Turquoise and Red Coral

Turquoise: CuAl6(PO4)4(OH)8·4H2O; Red Coral: Corallium rubrum (organic gemstone)

Chert (often called Flint in this context)

Silicon Dioxide (SiO2)

Chert (Cherty Limestone or Flint)

Microcrystalline Silica (SiO2)

Petrified Wood

Silicified Wood (primarily SiO2 - Silicon Dioxide)

Chert (Jasper/Flint variety)

Microcrystalline quartz (SiO2)

Amber

Succinite (Organic Mineraloid) - C10H16O

Fossiliferous Limestone

Calcium Carbonate (CaCO3) with fossil inclusions

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Arrowhead/Tool variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Iron-stained)

Microcrystalline quartz (SiO2)