Sedimentary (Cryptocrystalline Silica)

Agate / Banded Chalcedony

Agate (Silicon Dioxide / SiO2)

Quartz Vein in River Siltstone

Crystalline Quartz (SiO2) in Siliclastic Matrix

Geode (unopened nodule)

Silicon Dioxide (SiO2) Nodule

Chert (Common Opal/Jasper variety)

Microcrystalline Quartz (SiO2)

Clear Quartz

Silicon Dioxide (SiO2)

Amethyst (Geode/Druzy)

Silicon Dioxide (SiO2) with iron impurities

Quartz (Milky/Crystalline variety)

Silicon Dioxide (SiO2)

Opal

Hydrated amorphous form of silica (SiO2·nH2O)

Chert (specifically Tan/Gray Chert)

Microcrystalline quartz (SiO2)

Jasper

Silicon Dioxide (SiO2) with impurities

Clear Quartz

Silicon Dioxide (SiO2)

Clear Quartz Crystal

Silicon Dioxide (SiO2)

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Quartz (Milky or White Quartz)

Silicon Dioxide (SiO2)

Common Opal

Hydrated amorphous form of silica (SiO2·nH2O)

Sandstone

Clastic Sedimentary Rock (composed mostly of SiO2)

Sandstone Concretion

Sandstone (Sedimentary Rock) with silica or calcite cement

Black Opal

Amorphous Hydrated Silica (SiO2·nH2O)

Sandstone (Banded)

Clastic Sedimentary Rock (primarily SiO2 with Iron Oxide staining)

Banded Flint (Chert)

Silicon Dioxide (SiO2)

Jasper (Red/Green Brecciated)

Silicon Dioxide (SiO2) with iron oxide and chlorite inclusions

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Chert (Jasper/Agate variety)

Microcrystalline Quartz (SiO2)

Chert (Jasper/Flint variant)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Precious Opal in Matrix

Hydrated Silica (SiO2·nH2O)

White Opal (Common)

Hydrated Silica (SiO2·nH2O)

Jasper with Hematite inclusions

Silicon Dioxide (SiO2) with Iron Oxide (Fe2O3)

Chert (Pebble)

Microcrystalline silica (SiO2)

Turquoise (beads)

Turquoise; CuAl6(PO4)4(OH)8·4H2O

K2 Jasper (Beads)

Granodiorite with Azurite and Malachite

Chalcedony (variations like Agate or Jasper)

Chalcedony (SiO₂ - microcrystalline quartz)

Dendritic Agate (or Dendritic Opal)

SiO2 (for Agate), SiO2·nH2O (for Opal)

Red Jasper (possibly Carnelian)

Silicon Dioxide with Iron Oxide inclusions (SiO2 + Fe2O3)

Red Jasper

Silicon Dioxide with Iron Oxide (SiO2)

Yellow Jasper

Jasper (Silicon Dioxide, SiO2)

Jasper

Silicon dioxide (SiO2)

Jasper

Silicon Dioxide (SiO2) with iron oxide impurities

Chert (and Chalcedony)

Microcrystalline Quartz (SiO2)

Picture Jasper

Silicon Dioxide (SiO2) with iron oxide and clay inclusions

Quartz (Clear Quartz)

Silicon Dioxide (SiO2)

Chert (Chalcedony/Agate)

Microcrystalline Quartz (SiO2)

Banded Chert / Banded Jasper (likely a variety of Chert/Chalcedony)

Chert (microcrystalline quartz)