Ferruginous Sandstone (Ironstone Conglomerate fragments)
Ferruginous clastic sedimentary rock (SiO2 cemented by Fe2O3)
sedimentary
Category
Organic (Often Found By Beachcombers)
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Vesicular Basalt
Basalt with vesicular texture
igneous
Firewood (Wood Log)
Lignum (Plant tissue composed of cellulose and lignin)
Organic (Non-geological)
Quartz (Float/Abraded)
Quartz (SiO₂)
Mineral
Acicular Azurite (indicated by deep blue, fibrous/fuzzy appearance)
Azurite (Copper Carbonate Hydroxide) - Cu3(CO3)2(OH)2
mineral
Aventurine
Quartz (Aventurine variety)
Mineral
Amethyst
Silicon Dioxide (SiO2) with iron impurities
mineral
Limonite Concretion
Limonite (Hydrated iron(III) oxide-hydroxides, FeO(OH)·nH2O)
sedimentary
Jasper
Jasper (Silicified microcrystalline quartz) - SiO2
sedimentary
Jasper
Silicon dioxide, SiO2
Mineral
Green Calcite
Calcium Carbonate (CaCO3)
mineral
Kunzite
Spodumene (LiAlSi2O6), variety Kunzite
Mineral
Satin Spar (Gypsum)
Calcium Sulfate Dihydrate (CaSO4·2H2O)
mineral
Yellow Jasper (Iron-stained Quartzite/Chert)
Silicon Dioxide (SiO2) with Hydrated Iron Oxide (Goehite/Limonite) inclusions
sedimentary
Chert (Flint nodule)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Quartz Pebble
Quartz (Silicon Dioxide, SiO2)
mineral
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Amygdaloidal Basalt
Amygdaloidal Basalt (Mafic Volcanic Rock)
igneous
Quartzite
Quartzite (primarily Silicon Dioxide, SiO2)
metamorphic
Larimar
Pectolite, NaCa2Si3O8(OH)
gemstone
Sodalite
Na8(Al6Si6O24)Cl2
mineral
Chert
Microcrystalline Quartz (SiO2)
sedimentary
Rose Quartz
Silicon Dioxide (SiO2) with trace amounts of titanium, iron, or manganese
mineral
Scoria (Lava Rock)
Scoria (Vesicular Basaltic Glass/Rock)
igneous
Conglomerate
Conglomeratic Sandstone / Sedimentary Breccia
sedimentary
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Beryl (Variety: Aquamarine)
Beryllium Aluminum Cyclosilicate (Be3Al2Si6O18)
mineral
Fulgurite
Luechatelierite (SiO2 glass)
mineraloid
Gabbro (Water-worn pebble)
Gabbro
igneous
Prehnite
Prehnite (Ca2Al(AlSi3O10)(OH)2)
mineral
Pyrite
Iron Sulfide (FeS2)
mineral
Malachite with Chrysocolla
Copper carbonate hydroxide (Cu2CO3(OH)2) and Hydrated copper silicate (Cu,Al)2H2Si2O5(OH)4·nH2O
mineral
Smoky Quartz with Feldspar
SiO2 (Quartz) with KAlSi3O8 (Potassium Feldspar)
mineral
Labradorite
Feldspar (variety of Anorthite), (Ca,Na)(Al,Si)4O8
mineral
Quartzite (River Pebble)
Metamorphic Quartzite (SiO2)
metamorphic
Sandstone
Arenite
sedimentary
Coral Fossil (Favosites type)
Phylum Cnidaria, Class Anthozoa (often CaCO3 - Calcium Carbonate)
sedimentary
Chert / Flint
Microcrystalline or cryptocrystalline quartz (SiO2)
sedimentary
Concrete Fragment
Artificial Conglomerate (Cement and Aggregate)
sedimentary
Greenstone / Metagraywacke
Metamorphosed basaltic or sedimentary rock (Complex Silicate)
metamorphic
Serpentine (Greenstone)
Antigorite, Lizardite, and Chrysolite mixture (Mg3Si2O5(OH)4)
metamorphic