Greywacke
Greywacke (Lithofeldspathic Sandstone)
sedimentary
Category
Man Made
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Scoria (Lava Rock)
Scoria
igneous
Vesicular Basalt
Extrusive mafic igneous rock
igneous
Quartz (Milky/Common)
Silicon Dioxide (SiO2)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Citrine
Silicon Dioxide (SiO2) with iron impurities
mineral
Quartzite River Cobble
Quartzite (SiO2)
metamorphic
Black Jasper (Etched)
Silicon Dioxide (SiO2) with impurities
mineral
Quartzite River Rock
Quartzite (SiO2)
metamorphic
Red Jasper
Silicon Dioxide (SiO2)
sedimentary
Chert (Jasper variety)
Silicon Dioxide (SiO2)
sedimentary
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Unakite
Unakite (metamorphosed granite)
metamorphic
Seashell (Cockle Shell)
Cardiidae (Bivalvia), primary composition: Calcium Carbonate (CaCO3) in the form of aragonite or calcite
fossil
Quartz (Milky/Gold-stained)
Silicon Dioxide (SiO2)
mineral
Unakite
Epidotized Granite
metamorphic
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Milky Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Quartz (Milky Quartz)
Silicon Dioxide (SiO2)
mineral
Quartzite (River Stone)
Quartzite (SiO2)
metamorphic
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Red Sandstone
Arenite (Ferruginous Sandstone)
sedimentary
Moss Agate
Chalcedony (SiO2 with inclusions)
mineral
Amber (Cherry or Red variety)
Succinite (with various trace amounts of organic compounds)
Organic Gemstone (not a rock)
Yellow Citrine Quartz
Silicon Dioxide (SiO₂)
mineral
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Petrified Wood
Silicified wood (Quartz variant, SiO2)
sedimentary
Citrine
Silicon Dioxide (SiO2)
mineral
Porphyritic Andesite
Andesite (Intermediate Volcanic Rock)
igneous
Yellow Quartz River Pebble
Silicon Dioxide (SiO2)
mineral
River Quartz / Quartzite Pebbles
Quartzite (primarily Silicon Dioxide, SiO2)
metamorphic
Quartzite (River Pebble)
Quartzite (SiO2)
metamorphic
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Glauconitic Sandstone
Glauconitic Quartz Arenite
sedimentary
Chert (often called Flint)
Chert (Cryptocrystalline Silica, SiO2)
sedimentary
Agate (Nodule/Chert)
Silicon Dioxide (SiO2)
sedimentary
Sandstone with Iron Oxide Coating
Arenite (SiO2 with Fe2O3 impurities)
sedimentary
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Sandstone (Ferruginous)
Arenite (primarily SiO2 with Fe2O3/FeO(OH) cementing agents)
sedimentary
Amber
Succinite (with a generalized formula of C10H16O)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral