Synthetic Material (Not A Rock Or Mineral)

Coarse-grained granite or granitic pegmatite

Granite; primarily quartz (SiO₂), feldspar, and mica/amphibole

Red Sandstone

Clastic sedimentary rock (primarily SiO2 with Fe2O3 iron oxide staining)

Sandstone with Hematite staining

Arenite with Fe2O3 inclusions

Shale or Mudstone (Based on appearance)

Shale (fine-grained, laminated fissile sedimentary rock) / Mudstone (fine-grained, non-fissile sedimentary rock)

Biotite-bearing granite or granitic gneiss

Quartz–feldspar–mica rock; chiefly quartz (SiO₂), feldspars, and biotite mica

Mica Schist

Schist (Mica-rich Metamorphic Rock)

Quartz-rich rock with chlorite/epidote vein

Milky quartz with green chlorite or epidote; exact identification requires testing

Unakite

Unakitized granodiorite / Quartz-Epidote-Feldspar rock

Granite

Phaneritic Igneous Rock

Feldspathic Gneiss

High-grade Metamorphic Rock (Gneiss)

Seashell Fossil

Invertebrate fossil (phylum Mollusca)

Chert Nodules or Concretion

Cryptocrystalline Quartz (SiO2)

River Stone (likely Quartzite or Limestone)

Silicon dioxide (SiO2) or Calcium carbonate (CaCO3)

Chert (White Chert/Flint)

Microcrystalline Quartz (SiO2)

Bumblebee Jasper

Travertine (Calcite/Aragonite) with Realgar, Pyrite, and Volcanic Ash

Chert (Flint)

Microcrystalline quartz (SiO2)

Blue Opal Inlay (Simulated/Lab-created)

Hydrated Amorphous Silica (SiO2·nH2O) with polymer resin

Petrified Wood

Silicified Wood (SiO2)

Quartz-rich breccia or vein quartz with dark inclusions

Milky quartz (SiO₂), likely brecciated and cemented with iron oxides and dark mica/amphibole minerals

Limestone

Calcium Carbonate (CaCO3)

Likely tumbled quartz-rich pebble

Quartz (SiO₂), possibly a weathered quartzite or chalcedony pebble

Brecciated jasper, possibly rainforest jasper or brecciated rhyolite

Brecciated microcrystalline quartz (SiO₂), commonly called jasper; the green portions may contain epidote, chlorite, or iron-bearing silicates, while red-brown areas are typically hematite or other iron oxides

Possible tektite or dark volcanic rock fragment

Uncertain; likely natural silicate glass (tektite) or basalt

Sandstone Pebble

Arenite (primarily SiO2)

Petrified Wood

Silicified wood (Quartz/Chalcedony/Opal)

Basalt

Basalt

Granite-like rock

Felsic intrusive igneous rock, likely granite or granodiorite

Granite (Pink/Potassium Feldspar Granite)

Felsic Plutonic Rock (Potassium Feldspar, Quartz, Mica, and Amphibole)

Fossilized bivalve shell

Bivalvia indeterminate; likely a fossil cockle or clam shell, aragonite/calcite replaced or preserved

Gneiss

Gneiss

Iridescent schist or phyllite

Micaceous quartz-rich schist/phyllite, likely containing muscovite or chlorite

Brecciated quartz-rich rock, possibly silicified breccia

Silica-rich breccia; chiefly microcrystalline quartz (SiO₂), with possible calcite and iron-oxide staining

Weathered iron-rich sandstone or laterite fragment

Ferruginous sandstone, chiefly quartz (SiO₂) cemented or stained by iron oxides/hydroxides

Weathered quartz-rich rock, possibly chert or milky quartz

Mostly microcrystalline or crystalline quartz (SiO₂), identification uncertain from photograph

Chert (Flint)

Silicon dioxide (SiO2)

Muscovite Mica

Muscovite - KAl2(AlSi3O10)(F,OH)2

Diorite

Diorite (Intermediate intrusive igneous rock)

Sandstone

Sandstone (lithified quartz arenite, arkose, graywacke, etc. depending on composition)

Brachiopod Fossil in Limestone

Phylum Brachiopoda (likely Order Spiriferida), CaCO3 (Calcite)

Polished pink granite cobble

Granite, chiefly potassium feldspar, plagioclase, quartz, and biotite/hornblende

Jasper Agate (specifically Brecciated Jasper with Agate inclusions)

Silicon Dioxide (SiO2)

Sandstone

Arenite (composed primarily of SiO2)