Limestone (River or Sea Cobble)
Calcium Carbonate (CaCO3)
sedimentary
Category
Organic (Often Found By Beachcombers)
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Chert (White Chert)
Microcrystalline Quartz (SiO2)
sedimentary
Garden Quartz
Included Quartz (SiO2 with accessory minerals such as Chlorite, Hematite, or Feldspar)
mineral
Calcareous Tufa / Limestone Fragment
Calcium Carbonate (CaCO3)
sedimentary
Fossiliferous Limestone
Biomicrite / Limestone with fossils
sedimentary
Chert (Flint Pebbles)
Microcrystalline Quartz (SiO2)
sedimentary
Petrified Wood
Silicified Wood (primarily SiO2)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Sandstone with Algae Growth
Arenite with Chlorophyta/Lichen
sedimentary
Brown Pebble (Probable Chert or Siltstone)
Silicon Dioxide (SiO2) / Sedimentary Microcrystalline Quartz
sedimentary
Chert
Cryptocrystalline Quartz (SiO2)
sedimentary
Chert (Flint Nodules)
Silicon Dioxide (SiO2)
sedimentary
Glauconitic Sandstone
Glauconitic arenite (contains (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2)
sedimentary
Chert (Jasper variation)
Chert (Cryptocrystalline microcrystalline Silicon Dioxide, SiO2)
sedimentary
Petrified Wood
Silicified Wood (primarily SiO2)
fossil
Chert (specifically Jasper/Brown Chert)
Silicon Dioxide (SiO2)
sedimentary
Amber (Rough Baltics/Beach Specimen)
Succinicum (Organic Gemstone - Fossilized Resin)
mineral
Chert
Microcrystalline silica (SiO2)
sedimentary
Fossiliferous Limestone
Bioclastic Limestone (CaCO3)
sedimentary
Fossiliferous Limestone
Biogenic Limestone (Calcium Carbonate, CaCO3)
sedimentary
Chert (Flint)
Chert (Silicon Dioxide, SiO2)
sedimentary
Banded Chert
Silicon dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Moss Agate
Silicon Dioxide (SiO2) with inclusions
mineral
Amber (Copal)
Fossilized Tree Resin
mineraloid
Amber
Succinite (approximate formula C10H16O)
mineral
Glauconite Sandstone
Glauconitic Sandstone (K(Fe,Al)2(Si,Al)4O10(OH)2)
sedimentary
Chert (Nodule)
Microcrystalline quartz (SiO2)
sedimentary
Amber
Succinicum (Formula: C10H16O)
Mineraloid
Limestone (Tufa/Travertine)
Sedimentary Calcium Carbonate (CaCO3)
sedimentary
Chert (Jasper)
Microcrystalline Quartz (SiO2)
sedimentary
Banded Chert / Chalcedony
Silicon Dioxide (SiO2)
sedimentary
Chert (often called Flint)
Chert (Cryptocrystalline Quartz, SiO2)
sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
sedimentary
Sandstone Concretion
Sedimentary Clastic Rock (Silicate-rich)
sedimentary
Agatized Fossil (Druzy Agate)
Silicon Dioxide (SiO2) replacing organic matter
sedimentary
Pyrite (Fool's Gold) Cube
Iron Sulfide (FeS2)
mineral
Chert (Jasper/Agate variety)
Microcrystalline Quartz (SiO2)
sedimentary
Amber
Succinite (C10H16O)
mineral
Sandstone Concretion
Arenaceous concretion (primarily SiO2 with Fe2O3 staining)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Chert (Jasper/Flint variant)
Silicon Dioxide (SiO2)
sedimentary
Chert (varieties include Flint and Jasper)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary