Synthetic Material (Not A Rock Or Mineral)

Quartz (Iron-stained)

Silicon Dioxide (SiO2)

Tumbled dark stone, likely basalt or basaltic rock

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

Olivine/Peridot

Magnesium Iron Silicate (Mg,Fe)2SiO4

Red Sandstone

Arenite (Ferruginous Sandstone)

Coquina

Coquina (Bioclastic Limestone)

Sandstone with Calcite Vein

Clastic sedimentary rock (primarily SiO2) with Calcium Carbonate (CaCO3) infilling

Sandstone (Quartz-rich)

Arenite (composed primarily of SiO2)

Quartzite

Quartzite (primarily SiO2)

Diorite (possibly Orbicular Diorite or Porphyritic Diorite)

Intermediate Phaneritic Igneous Rock

River Pebble (Quartz/Jasper)

Silicon Dioxide (SiO2)

Greenstone (River Pebble)

Metabasalt / Greenschist

Sandstone with Iron Oxide

Arenite (SiO2 with Fe2O3 inclusions)

Chalcedony (Botryoidal or Agate nodule)

Silicon Dioxide (SiO2)

Chert Concretion

Microcrystalline Quartz (SiO2)

Red Sandstone

Arenite (Ferruginous Sandstone)

Quartz-bearing volcanic rock, likely vesicular basalt

Basalt with secondary quartz (SiO₂) and possible zeolite/chalcedony infill

Sandstone (with vugs or solution cavities)

Arenite (primarily Quartz and Feldspar with CaCO3 or SiO2 cement)

Sandstone (Quartzose type)

Arenite (primarily SiO2)

Weathered mica-rich metamorphic rock

Probable biotite schist or mica schist

Serpentinite

Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4

Quartzite River Cobble

Quartzite (primarily SiO2)

Sandstone

Sandstone (Arenite)

Weathered quartz-rich rock, possibly granite or quartzite

Indeterminate; likely quartz–feldspar aggregate, possibly granitic gneiss

Tumbled quartz-rich agate/geode fragment

Microcrystalline quartz (SiO₂), likely chalcedony with crystalline quartz and possible iron-oxide inclusions

Marble

Metamorphic rock composed of Recrystallized Carbonate Minerals (chiefly CaCO3)

Opal

Hydrous silicon dioxide (SiO2·nH2O)

Amethyst quartz crystal

Quartz, silicon dioxide (SiO₂), purple variety amethyst

Small quartz-rich pebble

Quartz (SiO₂), possibly quartzite or weathered granite fragment

Weathered granite (feldspathic, iron-stained granite)

Granite; primarily quartz, potassium feldspar, plagioclase feldspar, and minor mica/amphibole. Exact identification is uncertain from a single photograph.

Sandstone (Ferruginous/Banded)

Clastic Terrigenous Sandstone (SiO2 with Fe2O3 cement)

Iron-rich concretion or weathered ironstone

Goethite–hematite limonite aggregate; commonly described as limonite or ironstone

Gneiss

Gneiss

Dyed Agate

Silicon Dioxide (SiO2) - variety Chalcedony

River Rock

Sedimentary Rock (various compositions)

Polished basalt with a quartz vein

Basalt, cut by milky quartz (SiO₂)

Mica Schist

Mica Schist (Schistose metamorphic rock rich in Muscovite/Biotite)

Schist (Greenschist / Mica Schist)

Metamorphic rock rich in platy minerals (e.g., Chlorite/Mica schist)

Sandstone (Ferruginous/Red Sandstone)

Clastic sedimentary rock (primarily SiO2 with Fe2O3)

Red Jasper

Silicon dioxide (SiO2) with iron oxide (Fe2O3) inclusions

Quartz (specifically Milky or Clear Chunk)

Silicon Dioxide (SiO2)

Milky Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Weathered granite pebble

Granitic rock, chiefly quartz, potassium feldspar, plagioclase, and mica/hornblende