Not A Rock (Synthetic Material)

Sandstone

Arenite (SiO2 based with mineral cement)

Basalt with Quartz Veins

Basalt (with SiO2 veins)

Shale

Shale (clastic sedimentary rock)

Sandstone (Ferruginous)

Arenite (with Iron Oxide)

Sandstone

Arenite (SiO2, often with CaCO3 or Fe2O3 cement)

River cobble (Greywacke/Sandstone)

Sandstone / Greywacke

Dark igneous rock, likely basalt or diabase, with a second purplish specimen

Basalt/diabase; exact identification is uncertain from the photograph

Quartz-rich gravel fragment

Quartz (silicon dioxide, SiO₂), possibly with feldspar or carbonate inclusions

Serpentinite (likely veined variety)

Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), commonly with magnetite and carbonate veins

Basaltic Tuff / Volcanic Breccia

Pyroclastic Breccia / Lithic Tuff

Black Tourmaline

Schorl (Na(Fe²⁺)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄)

Sandstone (likely Greywacke or Lithic Sandstone)

Arenite / Wacke

Nephrite Jade

Nephrite

Mica-rich schist (likely muscovite schist)

Muscovite–quartz schist; chiefly muscovite mica, quartz, and minor feldspar/biotite

Concrete

Anthropogenic Conglomerate

Polished red jasper (likely brecciated jasper)

Microcrystalline quartz/chalcedony, SiO₂, colored mainly by iron oxides

River Rock

N/A - Generic term for water-smoothed rock

Sandstone

Sandstone (Sedimentary rock composed of silicate grains)

Tumbled quartz-rich pebble

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

Fossil bivalve or brachiopod in sedimentary rock

Unidentified fossil shell impression; likely a ribbed bivalve or brachiopod preserved in shale/siltstone

Tumbled blue-gray stone, likely basalt or slate

Probable fine-grained basalt; exact identification is uncertain from the photograph

Banded chert or agate

Microcrystalline quartz (chalcedony), SiO₂

Corundum

Corundum (Al2O3)

Textile (Upholstery Fabric)

Woven Polyethylene/Polyester or Cotton Blend

Sandstone

Arenite

Yellow Quartz Pebble

Silicon Dioxide (SiO2)

Sandstone (Ferruginous)

Arenite (primarily SiO2 with iron oxide Fe2O3 cement)

Quartz Pebble

Silicon Dioxide (SiO2)

Sandstone

Arenite (primarily SiO2)

Green Slag Glass (Cullet)

Amorphous Silica (Industrial Glass Byproduct)

Rounded weathered pebble

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

Red jasper in gray host rock (likely hematite-stained quartzite or rhyolite)

Jasper: microcrystalline quartz (SiO₂), with iron-oxide coloration; exact host uncertain from image

Chert / Jasper

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Small rounded pebble, possibly quartz-rich stone

Indeterminate; likely quartz/quartzite or a weathered feldspathic pebble

Stromatolite

Biogenic sedimentary rock

Exposed Aggregate Concrete (Pea Gravel)

Concrete with Siliceous Alluvial Gravels

Chert (Iron-stained)

Chert (SiO2)

Small pale stone, likely quartzite or limestone fragment

Indeterminate; possible quartzite (mostly SiO₂) or calcitic limestone (CaCO₃)

Dalmatian jasper (often sold as Dalmatian stone)

Porphyritic alkali feldspar–quartz syenite, commonly with black arfvedsonite/aegirine-group amphibole inclusions

Unknown Organic Object (likely a berry or fruit)

Not applicable; this is not a geological specimen. If it were a cranberry, its scientific name would be Vaccinium macrocarpon; if a cherry, it would be Prunus avium or Prunus cerasus.

Sandstone

Arenite (SiO2 primarily)