Chert (Black Chert / Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Quartzite Pebble
Quartzite (primarily SiO2)
metamorphic
Blue Lace Agate
Agate (Variety of Chalcedony, SiO2)
sedimentary
Moqui Marble
Iron Oxide Concretion (Limonite/Hematite shell with Sandstone core)
sedimentary
Carnelian Agate
Silicon Dioxide (SiO2) with Iron Impurities
mineral
Chert (Arrowhead/Tool Grade)
Microcrystalline Quartz (SiO2)
sedimentary
Agate (specifically Botswana or Lake Superior style chalcedony)
Silicon Dioxide (SiO2)
mineral
Bituminous Coal
Organic sedimentary rock (humic coal)
sedimentary
Sandstone (Flagstone)
Arenite (composed primarily of SiO2)
sedimentary
Turquoise in Matrix
Hydrous phosphate of copper and aluminium, CuAl6(PO4)4(OH)8·4H2O
mineral
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Jasper
Jasper (Silicified microcrystalline quartz) - SiO2
sedimentary
Quartzite Pebbles
Quartzite (primarily SiO2)
metamorphic
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Quartzite Pebble
Quartzite (primarily SiO2)
metamorphic
Quartz Pebble
Quartz (Silicon Dioxide, SiO2)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Quartz Pebble (often referred to as 'Sea Glass' or 'River Stone' when worn smooth)
Silicon Dioxide (SiO2)
mineral
Sandstone
Arenite (primarily Quartz, SiO2)
sedimentary
Granite (Orthoclase rich)
Granite (composed primarily of Quartz and Potassium Feldspar KAlSi3O8)
igneous
Chalcedony (Pink/Gray variety)
Silicon Dioxide (SiO2)
mineral
Jasper
Jasper (Silicon Dioxide, SiO2)
sedimentary
Olivine (Peridot)
Magnesium Iron Silicate (Mg, Fe)2SiO4
mineral
Diorite
Diorite (Intermediate intrusive igneous rock)
igneous
Quartz (Iron-Stained)
Silicon Dioxide (SiO2)
mineral
Gold Ore
Native Gold (Au)
mineral
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Quartz (Vein Quartz)
Silicon Dioxide (SiO2)
mineral
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Quartz Vein in Siltstone
SiO2 (Quartz) on clastic sedimentary matrix
sedimentary
Quartz Vein in Host Rock
Silicon Dioxide (SiO2) within Matrix
igneous/metamorphic
Quartz / Milky Quartz
Silicon Dioxide (SiO2)
mineral
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
metamorphic
Schist
Mica Schist
metamorphic
Serpentinite
Serpentinite (composed largely of serpentine group minerals including Antigorite, Lizardite, or Chrysotile)
metamorphic
Howlite and Purpurite druzy
Calcium Borosilicate Hydroxide (Howlite) and Manganese Phosphate (Purpurite)
mineral
Howlite and Purple Amethyst Druzy
Calcium Borosilicate Hydroxide (Howlite) and Silicon Dioxide (Quartz/Amethyst)
mineral
Fossil Coral (Rugose Coral Fragment)
Rugosa (extinct order of solitary and colonial corals)
sedimentary
Obsidian
Obsidian (Amorphous Volcanic Glass, SiO2)
igneous
Montana Moss Agate
Chalcedony (Silicon Dioxide, SiO2)
mineral
Red Jasper
Silicon Dioxide (SiO2) with iron oxide inclusions
sedimentary
Chalcedony with Druzy Quartz Geode
Silicon Dioxide (SiO2)
mineral