Organic Gemstone (Not A Rock)

Chert (Flint)

Chert (SiO2)

Fossiliferous Limestone (Coquina / Shell Limestone)

Biogenic Limestone (CaCO3)

Fossil Coral (Honeycomb Coral)

Favosites (extinct genus of Tabulate coral)

Chert (with Quartz vein)

Chert (Silicon Dioxide, SiO2)

Chert (specifically Flint or Jasper variant)

Silicon Dioxide (SiO2)

Chert (Tan/Yellow variety)

Microcrystalline quartz (SiO2)

Chert (or Flint)

Chert (Sedimentary Cryptocrystalline Sio2)

Turquoise in Matrix

Hydrated phosphate of copper and aluminium: CuAl6(PO4)4(OH)8·4H2O

Jasper (Brown Iron-Rich Variety)

Silicon Dioxide (SiO2) with Fe2O3 (Iron Oxide/Crystalline Quartz)

Shungite (Noble/Type II)

Non-crystalline carbon (Fullerene-bearing carbonaceous rock)

Ferruginous Sandstone (Ironstone)

Sedimentary rock with Limonite/Goethite cement

Limestone

Calcium Carbonate (CaCO3)

Yellow Chert (Jasper)

Microcrystalline Quartz (SiO2)

Anthracite Coal

Anthracite (Carbon-based organic sedimentary/metamorphic rock)

Coal (Anthracite)

Anthracite (Carbon-based organic sedimentary/metamorphic rock)

Druzy Quartz on Vesicular Basalt

Silicon Dioxide (SiO2) in an extrusive Mafic igneous host rock

Red Chert (Jasper)

Silicon Dioxide (SiO2)

Petrified Wood

Silicified Wood (primarily SiO2)

Chert (varietal: Jasper or Flint)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Rose Quartz

Silicon Dioxide (SiO2) with trace titanium, iron, or manganese

Chert (Arrowhead variety)

Chert (SiO2)

Chert (Cherty Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Digital Multimeter (Synthetic Object)

Digital Multimeter (DMM)

Chert (specifically Pink/Tan Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Jasper/Iron-stained Quartzite)

Silicon Dioxide (SiO2)

Mookaite Jasper

Silicified Radiolarite (SiO2)

White Topaz

Aluminum Silicate Fluoride Hydroxide; Al2SiO4(F,OH)2

Pearl and Garnet Glass

Calcium Carbonate (CaCO3) for pearl; Silicon Dioxide (SiO2) for glass

Chert (specifically Banded Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Yellow/Brown variety)

Chert (SiO2)

Serpentine

Antigorite, Lizardite, or Chrysotile (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4

Serpentine (variety: Serpentine Rock)

Antigorite, Lizardite, or Chrysotile; formula generally (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4

Petoskey Stone

Hexagonaria percarinata (Fossilized Rugose Coral)

Chert / Flint

Microcrystalline Quartz (SiO2)

Chert (Nodule/Pebble)

Chert (Silicon Dioxide, SiO2)

Petrified Wood

Silicified Wood (primarily Quartz/Chalcedony, formula SiO2)

Zebra Rock / Zebra Marble

Banded Limestone-Marble Transition

Fossiliferous Limestone (Coquina / Shell Limestone)

CaCO3 (Calcium Carbonate)

Coral Rock (Coquina)

Biogenic Limestone (Calcium Carbonate - CaCO3)

Natural Pearl (appearing in a jewelry setting)

Calcium Carbonate (mostly Aragonite), CaCO3 with Conchiolin

Lapis Lazuli

Lapis Lazuli (A metamorphic rock primarily composed of Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Chert (and Flint variant)

Microcrystalline or cryptocrystalline Quartz (SiO2)