Anthropogenic Material

Amazonite (green microcline feldspar)

Microcline, KAlSi₃O₈

Vesicular basalt (scoriaceous volcanic rock)

Basalt, chiefly plagioclase, pyroxene, and commonly olivine; vesicles may be lined with secondary minerals

Milky quartz pebble

Quartz (silicon dioxide, SiO₂)

Quartzite

Quartz-rich metamorphic rock; chiefly SiO₂

Biotite schist (likely graphite-bearing)

Mica schist; chiefly quartz + biotite mica, with possible graphite and feldspar

Limestone

Sedimentary rock composed mainly of calcium carbonate (CaCO3)

Coquina / Limonite-stained Limestone

Sedimentary Limestone with Iron Oxyhydroxide (FeO(OH)·nH2O)

Polished Ocean Jasper beads

Orbicular jasper (microcrystalline quartz, SiO₂), commonly sold as ocean jasper

Petrified Wood

Silicified wood (primarily SiO2 - Silicon Dioxide/Quartz)

Petrified Wood

Silicified Wood (SiO2)

Green Glass Cullet / Recycled Glass

Amorphous Silicon Dioxide (SiO2) with various metal oxides

Botryoidal chalcedony (likely white quartz/chalcedony)

Microcrystalline quartz, SiO₂; possibly partly altered carbonate or opaline silica

Jadeite (Jade)

NaAlSi2O6 (Sodium Aluminum Silicate)

Sandstone

Arenite

Granite

Granite

Rounded weathered pebble

Likely fine-grained sandstone, siltstone, or weathered volcanic rock; exact identification is uncertain from the image

Iron-rich weathered rock fragment

Indeterminate; likely limonite/goethite-bearing sandstone or lateritic ironstone

Sandstone (Ferruginous)

Arenite with Iron Oxide matrix

Iron-stained quartz-rich rock, possibly weathered granite or pegmatite

Quartz–feldspar rock with iron-oxide alteration; exact identification is uncertain from the photograph

Petrified Wood

Petrified Wood (Silicified Wood)

Carved Stone Turtle

Carved Soapstone and Quartz

Diamond (or diamond simulant)

C

Slag (Industrial Glass Slag)

Amorphous Silicate Glass (often containing Al, Ca, Mg, and Ti oxides)

Chert Pebble

Microcrystalline Quartz (SiO2)

Flint / Chert

Silicon dioxide (SiO2)

Flint Pebble

Sedimentary cryptocrystalline quartz (SiO2)

Micrometeorite (Spherule)

Extraterrestrial Accretion Spherule

Tumbled yellow quartz (likely citrine or iron-stained quartz)

Quartz, SiO₂; yellow color from trace iron or irradiation/heat-related coloration

Rounded brown pebble, likely weathered basalt or iron-rich chert

Indeterminate; possibly basalt (fine-grained mafic silicate rock) or ferruginous chert

Mudstone

Argillite / Siliciclastic sedimentary rock

Fossil oyster shell

Ostrea or Exogyra sp. (identification uncertain)

Serpentine

Serpentine group ((Mg,Fe,Ni,Al,Zn,Mn)3(Si,Al)2O5(OH)4)

Tumbled brown pebble

Indeterminate; likely quartz-rich sandstone or chert

Banded gneiss pebble

Biotite–quartz–feldspar gneiss (composition variable)

Petrified wood

Silicified wood, chiefly microcrystalline quartz (SiO₂)

Tumbled jasper or rhyolitic porphyry

Silicic volcanic rock, likely rhyolite (quartz- and feldspar-rich), possibly jasperized

Quartz / Quartzite

Silicon Dioxide (SiO2)

Sandstone

Arenite (primarily SiO2)

Sandstone (Tumbled/River Pebble)

Arenite (composed primarily of SiO2)

Limestone

Calcite (CaCO3)

Tumbled quartz-rich pebble

Likely milky quartz with a dark mafic inclusion or attached basalt; exact identification requires testing

Petrified Wood (Silicified Fossil)

Silicified Wood (SiO2)