Clear Quartz
Silicon Dioxide (SiO2)
mineral
Chert (often called Flint when dark)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Granite
Granite (Felsic Plutonic Rock)
igneous
Sandstone (Wonderstone)
Silicified Sandstone / Orthoquartzite with Liesegang rings
sedimentary
Basalt River Stones
Aphantic Mafic Igneous Rock (Basalt)
igneous
Diorite
Diorite (intermediate intrusive igneous rock)
igneous
Granite (Background) and Quartzite/River Pebble (Foreground Heart)
Phaneritic Felsic Igneous Rock (Granite background)
igneous
Quartzite with Iron Inclusions
Metamorphosed Sandstone (SiO2 dominated)
metamorphic
Quartz (Iron-stained)
Silicon Dioxide (SiO2)
mineral
Onyx (Black Onyx)
Silicon Dioxide (SiO2)
mineral
Yellow Quartz (Citrine or Quartz Crystal with Iron Inclusions)
Silicon Dioxide (SiO2)
mineral
Coral Fossil (Petrified Coral)
Scleractinia (Order) - Calcified Fossil Skeleton (CaCO3)
sedimentary
Basalt
Basalt (Mafic volcanic rock)
igneous
Chert (with Limestone matrix)
Chert (Silica: SiO2)
sedimentary
Limestone (specifically Marl or Chalk)
Calcium Carbonate (CaCO3)
sedimentary
Basalt
Basalt (Aphanitic Mafic Igneous Rock)
igneous
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Agate (Banded Chalcedony)
Agate (Silicon Dioxide, SiO2)
mineral
Sandstone
Sandstone (Sedimentary rock composed of silicate grains)
sedimentary
Quartz (Milky Quartz)
Silicon Dioxide (SiO2)
mineral
Conglomerate
Conglomerate (clastic sedimentary rock)
sedimentary
Granite
Phaneritic Acidic Igneous Rock (Granite)
igneous
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Ferruginous Quartz
Silicon Dioxide (SiO2) with iron oxide inclusions
mineral
Epidote
Epidote Group (Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH))
metamorphic
Green Sandstone
Glauconitic Sandstone
sedimentary
Jadeite
Jadeite (NaAlSi2O6)
metamorphic
Sandstone with Secondary Mineral Encrustation
Arenite with Silica/Calcite deposits (SiO2 or CaCO3)
sedimentary
Sandstone (likely Quartzose Sandstone)
Arenite (primarily SiO2)
sedimentary
Pumice
Pumice (a highly vesicular volcanic glass)
igneous
Pink Granite
Granite (Phaneritic Quartz-Feldspar Rock)
igneous
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Ferruginous Chert
Microcrystalline Quartz (SiO2) with Iron Oxides
sedimentary
Limonite (Iron Ore)
Limonite (Hydrous iron(III) oxide-hydroxide mixture, primarily FeO(OH)·nH2O)
mineral
Chert (Arrowhead/Tool variety)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Basalt (Weathered River Stone)
Basalt (Extrusive Mafic Igneous Rock)
igneous
Chert (Nodule)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Quartz in Matrix
Silicon Dioxide (SiO2)
mineral
Rough Diamond
Diamond (pure Carbon, C)
mineral
Chert (Jasper/Agate variety)
Microcrystalline Quartz (SiO2)
sedimentary
Ferruginous Quartz
Silicon Dioxide (SiO2) with Hematite/Limonite inclusions
mineral
Unakite
Epidotized Granite
metamorphic