Sedimentary (Microcrystalline Quartz)

Sandstone Pebble

Arenite (primarily Quartz, SiO2)

Purple Chalcedony (likely dyed Agate)

Silicon Dioxide (SiO2)

Banded Agate (likely Carnelian Agate or Sardonyx)

Agate is a common name for a microcrystalline variety of Quartz (SiO₂), specifically a form of Chalcedony.

Fossil Coral (Rugose Coral Fragment)

Rugosa (extinct order of solitary and colonial corals)

Limestone

Calcite (CaCO3)

Banded Agate (with Quartz Geode Center)

Silicon Dioxide (SiO2)

Quartzite River Cobble

Quartzite (SiO2)

Banded Gneiss with Quartz Vein

Foliated Metamorphic Rock (Gneiss)

Banded Black Onyx (Chalcedony)

Silicon Dioxide (SiO₂)

Quartz Geode

Silicon dioxide (SiO2)

Puddingstone (Jasper Conglomerate)

Jasper Conglomerate (SiO2 matrix with Fe2O3 inclusions)

Gowganda Tillite (Puddingstone)

Glacial Tillite (Diamictite) with Jasper inclusions

Conglomerate

Conglomerate (Sedimentary rock)

Sandstone (Graywacke)

Clastic Sedimentary Rock (Lithic Sandstone)

Quartz Druzy on Geode Fragment

Silicon Dioxide (SiO2)

Gneiss

Gneiss (Metamorphic rock)

Chalcedony (Agate/Blue Quartzite)

Silicon Dioxide (SiO2)

Limonite with Hematite

Limonite (FeO(OH)·nH2O) and Hematite (Fe2O3)

Jasper

Silicon Dioxide (SiO2) with impurities

Chert (often called Flint in various colors)

Silicon Dioxide (SiO2)

Slate

Foliated Metamorphic Rock

Clear Quartz

Quartz (Silicon Dioxide, SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Clear Quartz

Silicon Dioxide (SiO2)

Clear Quartz

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Clear Quartz

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Sandstone

Clastic sedimentary rock (primarily SiO2)

Chalcedony (specifically Agate or Carnelian variety)

Cryptocrystalline Silica (SiO2)

Chalcedony (Common Opal variant or Agate)

Silicon Dioxide (SiO2)

Quartzite (River Pebble)

Metamorphosed sandstone (SiO2)

Sandstone (with Iron Staining)

Clastic sedimentary rock (SiO2 with Fe2O3 impurities)

Sandstone

Arenite (composed primarily of SiO2)

Sandstone (Quartz Arenite)

Sandstone (Chemical formula: primarily SiO2)

Sandstone (Weathered)

Arenite (primarily SiO2)

Red Sandstone

Arenite with Hematite (Fe2O3) cement

Sandstone (Quartzite-rich)

Clastic Sedimentary Rock (primarily SiO2)

Quartz (Milky/Common)

Silicon Dioxide (SiO2)

Limonite

Limonite (FeOO·nH2O)