Synthetic Material (Not A Rock Or Mineral)

Weathered iron-rich rock, possibly basalt or ironstone

Indeterminate; likely Fe-oxide-bearing basaltic rock (commonly magnetite/hematite in a silicate matrix)

Red jasper (likely iron-rich chert)

Microcrystalline quartz (SiO₂), colored by hematite/goethite; possibly brecciated jasper

Probable serpentinite (serpentine-rich rock)

Serpentinite; chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with possible magnetite and olivine remnants

Milky Quartz in Conglomerate Matrix

Silicon Dioxide (SiO2) within Clastic Sedimentary Rock

Mica Schist

Mica Schist (predominantly Muscovite or Biotite sheet silicates)

Pebble Gravel Mix (Quartzite, Basalt, Chert)

Alluvial River Gravel / Aggregate Clasts

Pink granite pebble

Granite, composed mainly of quartz, potassium feldspar, plagioclase feldspar, and biotite/hornblende

Iron-stained quartz-bearing rock

Quartz (SiO₂), likely in a limonite/goethite-rich matrix

Granite

Granite (a common rock type, not a single mineral with a formula. Composed primarily of quartz, feldspar, and mica/amphibole).

White calcite (likely tumbled calcite or marble fragment)

Calcite, calcium carbonate (CaCO₃); if the specimen is granular and rock-like, it may be marble, a calcite-rich metamorphic rock

Quartz (Milky or White Quartz)

Silicon Dioxide (SiO2)

Fossilized Coral

Hexagonaria (Rugose coral) / Calcium Carbonate (CaCO3)

Polished Mexican “Crazy Lace” agate tower

Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide inclusions

Conglomerate

Conglomerate (SiO2 matrix with varying clasts)

Orange Calcite

Calcium Carbonate (CaCO3)

Pebble (river rock/beach pebble)

Pebble (clast size class)

Chert (Common Opal variant)

Microcrystalline Quartz (SiO2)

Green Greenstone / Celadonite-bearing Metamorphic Rock

Greenschist / Celadonite / Serpentinitic pebble

Milky Quartz

Silicon Dioxide (SiO2)

Sandstone

Sandstone (SiO2 dominated)

Quartzite Pebbler

Quartzite (SiO2)

Serpentine

Serpentine Group (Mg3Si2O5(OH)4)

Weathered limestone

Calcite-rich limestone (CaCO₃), possibly fossiliferous or dolomitic

Polished red gemstone pendant, likely red jasper or brecciated jasper

Jasper: microcrystalline quartz (SiO₂), commonly with hematite or iron-oxide inclusions

Blue Goldstone

Aventurine Glass

Diorite (Salt and Pepper Rock)

Phaneritic Plutonic Diorite (Plagioclase Feldspar + Amphibole/Biotite)

Quartz Pebble (with Hematite/Feldspar Inclusions)

Silicon Dioxide (SiO2)

Lapis lazuli and green-blue chalcedony jewelry

Lapis lazuli: lazurite-bearing metamorphic rock, chiefly lazurite (Na₃Ca(Al₃Si₃O₁₂)S) with calcite and pyrite; second stone: likely chrysoprase or green-blue chalcedony (microcrystalline quartz, SiO₂)

Water-worn basalt cobble

Basalt; chiefly plagioclase feldspar, pyroxene, and minor olivine/iron oxides

Diorite

Intermediate Phaneritic Igneous Rock

Pink-and-gray quartz-rich pegmatite, possibly rose quartz with feldspar

Quartz (SiO₂) with K-feldspar/plagioclase; likely pegmatitic granite

Generic Rock / Pebble

Undetermined rock specimen

Sandstone (Quartzose)

Arenite (primarily SiO2)

Sandstone

Sandstone (lithified sand)

Laterite

Laterite (no specific mineral formula as it's a rock type)

Petrified Wood

Silicified Wood (SiO2)

Polygenetic Conglomerate (or Breccia)

Clastic Sedimentary Rock

Sandstone (Ferruginous)

Clastic sedimentary rock (primarily SiO2 with Fe2O3 cement)

Likely weathered quartz-bearing rock (uncertain identification)

Possibly quartz-rich granite or granitic aplite; exact identification requires a clearer, larger image and tests

Chert nodules in Limestone

Microcrystalline Quartz (SiO2) in Calcium Carbonate (CaCO3) matrix

Iron-stained quartz-rich rock, possibly jasper/quartzite

Quartz (SiO₂) with iron-oxide staining; likely ferruginous quartzite or jasper

Weathered quartz-rich rock, likely silicified limestone or quartzite

Microcrystalline quartz (SiO₂), possibly with calcite (CaCO₃) and iron-oxide staining