Sedimentary Rock (Technically A Microcrystalline Quartz Mineral Aggregate)

Ferruginous Sandstone (Ironstone)

Arenite with Iron-Oxide Cement (FeO(OH)·nH2O / Fe2O3)

Banded Agate

Cryptocrystalline Quartz (SiO2)

River Rock (Greywacke/Sandstone)

Lithic Wacke

Sandstone (Quartzite-rich)

Clastic sedimentary rock (SiO2 primary)

Chert / Flint

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Chert (White/Gray variety)

Chert (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Dragon Blood Jasper

Epidote with Pietersite or Red Jasper (Ca2Al2Fe3+[Si2O7][SiO4]O(OH))

Jasper (Red Jasper)

Silicon Dioxide (SiO₂)

Chert (specifically Flint)

Chert (Microcrystalline or Cryptocrystalline Quartz, SiO2)

Chert (White/Light Tan)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Sandstone (likely Quartz Sandstone)

Arenite (SiO2 based)

Chert (often called Flint or Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Nodule)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Cherty Shale / Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Jasper-rich)

Microcrystalline/Cryptocrystalline Quartz (SiO2)

Chert (variations include Flint or Jasper)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Chert (Nodule)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Basalt

Basalt (composition of plagioclase feldspar and pyroxene)

Milky Quartz

Quartz (Silicon Dioxide - SiO2)

Tiger's Eye

Tiger's Eye (a variety of Chalcedony, which is a microcrystalline quartz with fibrous inclusions of oxidized crocidolite)

Boxwork Siderite or Sepatarian Nodule Weathering

Siderite (FeCO3) with secondary mineralization or Boxwork Geode fragment

Chert (Tan/Grey)

Chert (Silicon Dioxide, SiO2)

Obsidian

Volcanic Glass (Amorphous Silica)

Chert (Flint)

Chert (SiO2)

Clear Quartz

Silicon Dioxide (SiO2) / Rock Crystal

Sandstone (with Iron Staining)

Clastic sedimentary rock (primarily SiO2 with Fe2O3 oxides)

Quartz (Iron-stained)

Silicon Dioxide (SiO2)

Chert (Jasper/Iron-stained Quartzite)

Silicon Dioxide (SiO2)

Obsidian

Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)

Milky Quartz (Vein Quartz)

Silicon Dioxide (SiO2)

Banded Agate

Microcrystalline Quartz (SiO2) with impurities

Chert (variations include Flint/Jasper)

Chert (SiO2)

Quartz

Quartz (SiO2 - Silicon Dioxide)

Quartzite with Quartz Vein

Metamorphosed Quartz-rich Arenite (SiO2)

Basalt (Amygdaloidal)

Amygdaloidal Basalt

Herkimer Diamond (Quartz)

Silicon Dioxide (SiO2)

Sandstone

Sandstone (arenite is a more specific geological term for a clean sandstone, while wacke refers to a dirty sandstone with significant matrix)

Granite

Granite (Felsic Plutonic Rock)

Chert (Flint)

Chert (microcrystalline quartz)

Limonite Concretion

Goethite-rich Concretion (FeO(OH))