Organic Material (Likely A Fruit Or Berry)

Coal (Bituminous)

Organic sedimentary rock primarily consisting of carbon (C)

Coquina / Fossiliferous Limestone

Coquina (composed primarily of Calcium Carbonate / CaCO3)

Quartz Crystal Cluster

Quartz (Silicon Dioxide, SiO2)

Rounded iron-rich pebble

Likely hematite/goethite-bearing quartzite or ironstone; exact identification requires testing

Greenstone / altered mafic rock

Likely chlorite–actinolite metabasalt (greenschist); exact identification requires testing

Weathered chert or silicified limestone nodule

Microcrystalline quartz (SiO₂), possibly replacing limestone; exact identification requires testing

Weathered sandstone pebble

Quartz-rich sandstone, likely ferruginous sandstone

Tufa (Calcareous Tufa)

Calcareous Tufa (CaCO3)

Sandstone (likely Arkosic or Quartzose)

Sandstone (SiO2 with inclusions)

Likely basaltic volcanic rock

Basalt, chiefly plagioclase feldspar and clinopyroxene, with possible olivine or iron oxides

Banded Chert

Microcrystalline silicon dioxide (SiO2)

Dendritic Agate (or Dendritic Opal)

SiO2 (for Agate), SiO2·nH2O (for Opal)

Chert (specifically Flint or Jasper variant)

Microcrystalline or Cryptocrystalline Silicon Dioxide (SiO2)

Iron-rich slag or limonite-bearing rock

Hydrated iron oxides, chiefly limonite/goethite (FeO(OH)·nH₂O); possibly industrial iron slag

Chert (Arrowhead Shard)

Microcrystalline silica (SiO2)

Petrified Wood

Silicified Wood / Xylopal

Chert (Jasper/Flint variety)

Microcrystalline quartz (SiO2)

Black Beach Pebble (Basalt / Slate Pebble)

Rounded Fine-Grained Clastic / Igneous Rock Pebble

Chert (Brown Chert / Flint)

Silicon Dioxide (SiO2)

Coprolite

Fossilized Feces

Petrified Wood

Silicified wood (Quartz replacement of organic wood structure)

Petrified Wood

Silicified Wood (SiO2)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Tumbled pink feldspar (likely orthoclase or microcline)

Potassium feldspar, KAlSi₃O₈

Quartz-rich metallic sulfide ore (probable pyrite-bearing rock)

Pyrite, FeS₂, in a quartz-rich host; exact identification is uncertain from the image

Tumbled green stone, likely serpentine

Serpentinite; principally serpentine-group minerals, Mg₃Si₂O₅(OH)₄

Likely weathered basalt or iron-rich volcanic rock

Basalt; primarily plagioclase feldspar, pyroxene, and possibly olivine with iron-oxide alteration

Chert (Jasper variety)

Chert (SiO2)

Quartz vein in dark host rock

Quartz (SiO₂), likely in basalt, gabbro, or altered mafic rock

Geode fragment, likely quartz-lined basalt or chalcedony nodule

Microcrystalline quartz (SiO₂), possibly with iron-oxide staining in a basaltic host

Tumbled dark stone, likely basalt or basaltic rock

Fine-grained mafic igneous rock; commonly basalt, composed mainly of plagioclase and pyroxene with possible olivine

Likely quartz-rich pebble (possibly weathered quartzite)

Quartzite; predominantly SiO₂ (identification tentative from photograph)

Polished orbicular jasper (likely ocean jasper)

Silicified microcrystalline quartz/chalcedony (SiO₂), with iron-oxide and other mineral inclusions

Pink quartz (likely rose quartz)

Quartz, silicon dioxide (SiO₂)

Polished blue stone, likely sodalite

Sodalite, Na₈(Al₆Si₆O₂₄)Cl₂; possibly blue-dyed jasper or lapis lazuli

Likely polished basalt with pale mineral inclusions

Basalt; inclusions possibly calcite, quartz, or weathered feldspar

Weathered river stones, likely basaltic andesite and related volcanic rocks

Fine-grained mafic/intermediate volcanic rocks; commonly basalt (plagioclase + pyroxene ± olivine) or andesite (plagioclase + pyroxene ± amphibole)

Likely purple quartzite or purple chert

Quartzite/chert, predominantly microcrystalline SiO₂; exact identification requires testing

Chert (variously known as Flint or Jasper)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Tektite (likely Australite)

Tektite (no specific chemical formula as it's a natural glass of variable composition, mostly SiO2, Al2O3, FeO, MgO, CaO, K2O, Na2O, TiO2)

Rounded sandstone pebble

Quartz-rich sandstone (commonly arkosic or feldspathic sandstone)

Iron-rich quartzite or silicified ironstone

Quartz (SiO₂) with iron oxides/hydroxides, likely limonite/goethite and possibly hematite