Sedimentary (Man Made)

Chert Pebble

Microcrystalline Quartz (SiO2)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chert / Flint

Cryptocrystalline quartz (SiO2)

Chert (specifically Jasper or Flint)

Cryptocrystalline Quartz (SiO2)

Chert (Jasper variation)

Microcrystalline Quartz (SiO2)

Coquina

Bioclastic Limestone (Coquina)

Chert (varieties include Flint and Jasper)

Silicon Dioxide (SiO2)

Chalk

Calcium carbonate (CaCO3)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chalk

Calcium Carbonate (CaCO3)

Siltstone Pebble

Siltstone (composed of microscopic quartz and clay minerals)

Concrete-like aggregate surface with embedded rock fragments

Anthropogenic concrete or exposed aggregate; not a natural rock specimen

Coal (Bituminous Coal)

Caustobiolith / Sedimentary Rock

Blue Chalcedony

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Turquoise-style beaded bracelet

Turquoise, hydrated copper–aluminum phosphate: CuAl₆(PO₄)₄(OH)₈·4H₂O; possibly dyed or composite beads

Chert (flint)

Microcrystalline quartz (SiO₂), commonly called chert; brown varieties may be termed brown flint

Chert (varieties: Flint or Jasper)

Silicon dioxide (SiO2) / Microcrystalline Quartz

Chalcedony with iron-oxide staining

Microcrystalline quartz (SiO₂), likely chalcedony or chert with limonite/goethite staining

Limestone

Calcareous sedimentary rock (CaCO3)

Chalcedony (Common Opal or Agate variant)

Silicon dioxide (SiO2) with trace hydration

Marble

Recrystallized Calcite (CaCO3)

Sandstone Pebble

Ferruginous Sandstone (SiO2 with Fe2O3)

White pebbles (rock material not identifiable from the image)

Undetermined; the smooth, pale pieces could be quartz, quartzite, or another light-colored rock

Chert (often called Flint in archaeological contexts)

Silicon Dioxide (SiO2)

Chert

Microcrystalline Quartz (SiO2)

Chert (Polished River Pebble)

Chert (SiO2)

Chert (Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Yellow Jasper/Flint pebble)

Microcrystalline Quartz (SiO2)

Tumbled brown chalcedony or jasper

Microcrystalline quartz, SiO₂; possibly iron-bearing jasper

Hoodoo (Limestone / Siltstone Formation)

Claron Formation (Sedimentary Rock - Limestone, Mudstone, Dolomite)

Turquoise

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

Slate

Metamorphic Pelitic Rock

Limestone

Sedimentary Rock (Primarily CaCO3)

Chert / Flint

Silicon Dioxide (SiO2)

Flint (chert) nodule

Microcrystalline quartz (SiO₂), a variety of chert

Chert (Nodule)

Chert (Silicon Dioxide, SiO2)

Chert (Flint)

Microcrystalline Silica (SiO2)

Jasper

Microcrystalline Quartz (SiO2)

Flint

Microcrystalline Quartz (SiO2)

Chert / Flint

Microcrystalline Quartz (SiO2)

Banded Chert (River Stone)

Silicon Dioxide (SiO2)

Chert (Nodule)

Microcrystalline Quartz (SiO2)