Sedimentary (Chemically Precipitated) Or Metamorphic

Yellow Quartz (Citrine/Yellow Jasper mix)

Silicon Dioxide (SiO2)

Yellow Chalcedony (Agate/Carnelian variant)

Silicon Dioxide (SiO₂)

Chert (variously Flint or Jasper gravel)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Chert (Septarian Nodules / Weathered Silex)

Microcrystalline Quartz (SiO2)

Schist

Mica Schist

Chert (Iron-stained)

Chert (primarily Microcrystalline Quartz, SiO2)

Chert (often called Flint when dark)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Ironstone Concretion (Limonite/Goethite)

Ferruginous Sandstone or Limonite (FeO(OH)·nH2O)

Gneiss

Gneiss (High-grade Metamorphic Rock)

Limestone

Calcium Carbonate (CaCO3)

Jasper Conglomerate (Puddingstone)

Siliceous Conglomerate (Quartz and Jasper clasts in a fine-grained matrix)

Granitic Gneiss

Gneiss (High-grade regional metamorphic rock)

Fluorite Octahedron

Fluorite (Calcium Fluoride, CaF2)

Limestone

Calcium Carbonate (CaCO3)

Dalmatian Stone

Peralkaline Quartz-Feldspar Porphyry with Arfvedsonite

Folded Schist / Gneiss (Metamorphic Rock)

Regional Metaphoric Folded Outcrop (predominantly Schist/Gneiss)

Quartz Pebble

Silicon Dioxide (SiO2)

Howlite and Purpurite druzy

Calcium Borosilicate Hydroxide (Howlite) and Manganese Phosphate (Purpurite)

Snowflake Obsidian

Vitreous Volcanic Glass (Siliceous Obsidian with Cristobalite inclusions)

Quartz (specifically Quartzite or Massive Quartz)

Silicon Dioxide (SiO2)

Limonite after Pyrite (Pseudomorph)

FeO(OH)·nH2O following FeS2

Quartz (Iron-stained or Milky Quartz)

Silicon Dioxide (SiO2)

Mahogany Obsidian

Volcanic Glass with Hematite/Magnetite inclusions

Marble

Recrystallized Calcite / Dolomite (CaCO3)

Sandstone

Arenite (SiO2 based with various mineral cements)

Concrete

Anthropogenic Sedimentary Rock (Hydrated Calcium Silicate)

Slate

Foliated Metamorphic Rock (primarily composed of quartz, illite, and chlorite)

Mica Schist

Foliated Metamorphic Rock (rich in Muscovite or Biotite)

Gneiss (specifically Micaceous Gneiss)

Gneiss (High-grade Regional Metamorphic Rock)

Chert (Jasper)

Silicon Dioxide (SiO2)

Chert (Tan/Brown variety)

Chert (Silicon Dioxide, SiO2)

Chert (often called Flint in this context)

Silicon Dioxide (SiO2)

Laterite

Laterite (Ferricrete)

Chert / Flint

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Jasper / Chert (River Pebble)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Chert (Nodule)

Silicon Dioxide (SiO2)

Chert / Flint

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Tan/Brown variety)

Chert (Microcrystalline Quartz, SiO2)

Chert / Flint

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Nodular or Massive Variety)

Cryptocrystalline Quartz (SiO2)

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Chert (Iron-stained)

Silicon Dioxide (SiO2)