Rock (Likely Sedimentary)

Unidentified gravel and stone fragments

Mixed, indeterminate lithologies; likely quartz, feldspar, and weathered silicate rock fragments

River Stones (Quartzite and Sandstone)

Quartzite / Sedimentary Rock (SiO2 dominant)

Sandstone (with manganese staining)

Clastic sedimentary rock (primarily SiO2)

River Stone (Quartzite/Chert)

Metamorphosed Quartz-rich Sedimentary Rock

Sandstone (with banding/weathering)

Clastic Sedimentary Rock (primarily SiO2)

Weathered iron-rich rock, possibly laterite or limonite-bearing sandstone

Iron oxides/hydroxides, chiefly limonite/goethite (FeO(OH)·nH₂O), with a probable silicate or clay matrix

Quartz / Common Opal

Silicon Dioxide (SiO2)

Sedimentary rock with quartz veining

Laminated siltstone or mudstone with hydrothermal quartz veins

Weathered sandstone or iron-stained sedimentary rock

Quartz-rich sandstone, likely limonitic/goethitic cement

Sandstone (likely a river or beach pebble)

Sandstone (a clastic sedimentary rock)

Coal (most likely Bituminous or Anthracite)

Coal (organic sedimentary rock)

Weathered brown rock, likely sandstone

Quartz-rich sandstone (composition uncertain from image)

Likely weathered iron-rich breccia or jasper

Silicified iron-oxide breccia; exact identification requires testing

Sandstone (Micaceous)

Arenite (composed primarily of SiO2)

Rounded quartz-rich river cobble (probable rhyolite/granite-derived stone)

Indeterminate felsic igneous cobble; likely quartz–feldspar aggregate with minor iron oxides

Polished brecciated jasper

Jasper, microcrystalline quartz (SiO₂), with iron-oxide and pale silica-rich fragments

Druzy Quartz on Limestone

Silicon Dioxide (SiO2) on Calcium Carbonate (CaCO3)

Weathered sandstone or siltstone pebble

Indeterminate siliciclastic sedimentary rock, likely quartz-rich sandstone (SiO₂-dominated)

Breccia Pebble

Sedimentary Breccia

Ferruginous Siltstone or Mudstone

Ferruginous Siltstone / Goethitic Sandstone

Weathered sandstone pebble

Quartz-rich sandstone, likely ferruginous sublitharenite

Rounded gray river pebble

Likely quartz-rich metamorphic or igneous pebble; exact identification requires testing

Quartz-rich rock, possibly milky quartz vein material

Quartz (SiO₂), likely with iron-oxide staining and minor host-rock inclusions

Rounded brown river pebble

Indeterminate lithic clast; possibly weathered sandstone or fine-grained volcanic rock

Weathered iron-rich sedimentary rock (probable laterite/ironstone)

Limonite/goethite-rich ferruginous material; commonly approximated as FeO(OH)·nH₂O with clay and quartz

Calcite on Limestone

Calcium Carbonate (CaCO3) on Sedimentary Rock

Chert (Chalcedony/Agate)

Microcrystalline Quartz (SiO2)

Smooth gray river pebble

Likely fine-grained sandstone or siltstone; exact identification requires a fresh surface and tests

Tumbled tan pebble, likely sandstone or chert

Uncertain; probable quartz-rich sandstone (SiO₂-bearing)

Limestone (specifically Grainstone or Micrite)

Calcium Carbonate (CaCO3)

Weathered stone nodule or concretion

Unidentified lithic concretion; composition cannot be determined from the image

Blue Agate (Dyed)

Silicon Dioxide (SiO2)

Quartzite in Conglomerate

Clastic Sedimentary Rock with Silicon Dioxide (SiO2) inclusions

Exposed aggregate concrete (stone-chip surface)

Portland-cement concrete containing natural aggregate; not a natural rock

Banded Sandstone Peabble

Arenite with iron oxide banding

Sandstone (likely Fossiliferous Sandstone)

Clastic sedimentary rock (primarily SiO2)

Gray metamorphic rock, likely gneiss or schist

Quartz–feldspar–mica metamorphic rock; exact identification requires a fresh surface and tests

Sandstone-based Concrete Fragment

Cementitious Composite with Sedimentary Aggregate

Sandstone (River Cobble)

Clastic sedimentary rock (primarily SiO2)

Sandstone (Weathered Pebble)

Arenite (SiO2 primarily)

Fossil Crab

Decapoda (likely Avitelmessus or Raninidae family)

Weathered schist or phyllite

Mica schist/phyllite, likely quartz–mica-rich metamorphic rock