Sedimentary Rock (Possibly A Conglomerate Or Coarse Grained Sandstone)

Rounded river cobble, likely quartz-rich sandstone or quartzite

Indeterminate quartz-rich clastic rock; probable sandstone (SiO₂-rich)

Weathered quartz-rich rock, possibly quartzite or granitic pegmatite fragment

Quartz (SiO₂)-dominant aggregate; exact identification is uncertain from the photograph

Rounded gray pebble (likely fine-grained volcanic or sedimentary rock)

Undetermined from image; possibly andesite or a fine-grained sandstone

Breccia

Clastic Breccia (SiO2/CaCO3 dominated)

River Rock

Sedimentary Rock (various compositions)

Gneiss

Gneiss (foliated metamorphic rock)

Likely weathered river pebble

Indeterminate lithology; possibly fine-grained sandstone, siltstone, or chert

Weathered limestone

Limestone; predominantly calcite (CaCO₃)

Weathered brown rock fragment

Indeterminate; possibly ferruginous sandstone or weathered volcanic rock

Sandstone

Arenite

Weathered granite or granitic gneiss

Quartz–feldspar–mica granitic rock; possibly weakly foliated gneiss

Foliated metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss, possibly migmatitic gneiss

Rounded granite or granitic gneiss cobble

Granite–gneiss, chiefly quartz, feldspar, and mica

Weathered sedimentary cobble, likely limestone or calcareous sandstone

Indeterminate carbonate-rich clastic rock; possibly micritic limestone or calcarenite

Granite Gneiss

Gneiss (derived from granitic protolith)

Conglomerate

Quartz Conglomerate

Conglomerate (River Rock)

Clastic sedimentary rock (primarily SiO2)

Likely weathered sandstone or fine-grained granite

Quartz–feldspar-rich lithic rock; exact identification requires a fresh surface and testing

Likely weathered quartz-bearing rock fragment

Provisional identification: quartz-rich sandstone or microcrystalline quartz (SiO₂)

Asphalt Concrete

Bituminous conglomerate

Granite Gneiss

Metamorphic Rock (Quartz, Potassium Feldspar, Plagioclase, Biotite/Amphibole)

Quartzite / Sandstone

SiO2 (Silicon Dioxide)

Iron-rich sandstone or ferruginous quartzite

Hematite/goethite-bearing quartz sandstone; possibly weakly metamorphosed to quartzite

Weathered sandstone pebble

Quartz-rich sandstone; predominantly SiO₂ grains cemented by silica, calcite, or iron oxides

Brown quartz-rich pebble (likely chert or weathered quartzite)

Quartz (SiO₂), possibly microcrystalline quartz/chert or quartzite

Black granite (likely polished gabbro or diabase)

Granitoid rock dominated by feldspar, quartz, and dark mafic minerals; exact identification requires testing

Conglomerate

Polymictic Conglomerate

Banded Gneiss

Gneiss (SiO2-rich metamorphic rock)

Sandstone (Quartzose / Feldspathic Sandstone)

Arenite (SiO2 principal matrix)

Breccia

Breccia (Clastic Sedimentary Rock)

Rounded sandstone pebble

Sandstone, commonly quartz–feldspar-rich arenite

Conglomerate

Polymictic conglomerate, likely carbonate-cemented

Rounded dark pebble, possibly weathered basalt

Fine-grained mafic volcanic rock; likely basalt, but identification is uncertain from the photograph

Breccia

Clastic Breccia (General mineral composition depends on fragments, often SiO2 or CaCO3)

Concrete fragment with Aggregate

Anthropogenic Concrete with Calcarious and Siliceous Aggregate

Sandstone pebble

Sandstone (mainly Quartz, SiO2)

Small tan rock fragment

Indeterminate; possibly quartz-rich sandstone or iron-stained quartz

Weathered granitic rock

Granitoid, likely biotite granite or granodiorite

Sandstone

Quartz Sandstone (predominantly)

Volcanic breccia or conglomeratic volcanic rock

Lithic volcanic breccia; possibly andesitic–basaltic matrix with feldspar-rich clasts

Likely weathered quartz-rich rock fragment

Uncertain; possibly quartz sandstone or a pale feldspathic rock

Rounded river cobble, likely weathered sandstone or quartzite

Indeterminate clastic silicate rock; possibly quartz-rich sandstone (SiO₂-dominant)