Sedimentary Rock (Possibly A Conglomerate Or Coarse Grained Sandstone)

Tumbled sandstone pebble

Quartz-rich sandstone, likely ferruginous sandstone

Iron-stained quartz-rich rock, possibly weathered sandstone

Quartz-rich sandstone with limonite/goethite staining; exact identification requires testing

Conglomerate

Polymictic conglomerate; clast-bearing sedimentary rock cemented by silica, calcite, or iron oxides

Concrete-like aggregate surface with embedded rock fragments

Anthropogenic concrete or exposed aggregate; not a natural rock specimen

Weathered granite or granitic gneiss

Quartz–feldspar–mica granitic rock; possibly gneiss if foliation is present

Banded chert or silicified sedimentary rock

Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and other mineral bands

Quartz-rich sandstone or quartzite pebble

Likely quartz arenite sandstone; possibly low-grade quartzite, composed mainly of SiO₂

Weathered granite or granitic gneiss

Granite; chiefly quartz, feldspar, and mica (possibly gneissic if foliation is confirmed)

Gneiss (or Granite Gneiss)

Metamorphic rock rich in quartz, feldspar, and biotite/amphibole

Sandstone

Arenite

Weathered gneissic rock

Biotite–quartz–feldspar gneiss, possibly migmatitic

River Pebble (Granite/Sandstone Pebble)

Rounded Quartz/Feldspar Gravel Clast

Mixed river stones and gravel

Polymictic alluvial clasts; individual pieces may include quartzite, granite, basalt, sandstone, limestone, and slate

Sandstone (likely Graywacke or Lithic Arenite)

Clastic sedimentary rock predominantly composed of silicate grains

Rounded brown cobble, likely weathered sandstone or iron-rich sedimentary rock

Indeterminate; possibly ferruginous sandstone or ironstone

Sandstone with trace fossil

Sandstone, possibly with Skolithos or similar trace fossil

Rounded gray river pebble, likely fine-grained sandstone or siltstone

Indeterminate clastic sedimentary rock; possibly quartz-rich sandstone or siltstone

Conglomeratic breccia

Clast-supported polymictic conglomerate/breccia, cemented by silica- or carbonate-rich matrix

Weathered iron-rich sandstone or ferruginous conglomerate

Quartz-rich sandstone cemented by iron oxides/hydroxides (primarily hematite and goethite)

Breccia

Sedimentary Breccia

Weathered reddish granite or granitic gneiss

Granite; mainly quartz (SiO₂), feldspar, and mica, possibly with iron-oxide staining

Weathered sandstone or iron-stained quartzite pebble

Likely quartz-rich sandstone (mostly SiO₂), possibly weakly metamorphosed quartzite

Conglomerate

Lithified, poorly sorted gravel; composition is uncertain from the image

Weathered quartz-bearing rock, possibly iron-stained quartzite

Quartzite (mostly SiO₂), tentatively identified

Conglomerate

Polymictic Conglomerate

Red Granite

Phaneritic Felsic Igneous Rock (Granite)

Yellow Quartzite

Silicon Dioxide (SiO2)

Weathered sandstone or quartzite cobble

Quartz-rich sandstone; possibly weakly metamorphosed quartzite (SiO₂-dominant)

Gneiss (possibly migmatitic or strongly folded banded gneiss)

Banded quartz–feldspar–mica gneiss; variable composition, commonly quartz + plagioclase/alkali feldspar + biotite/muscovite ± amphibole

Weathered rock fragment (likely granite or quartz-rich sandstone)

Uncertain; possible granitic fragment containing quartz and feldspar

Ferruginous Sandstone (Ironstone Conglomerate fragments)

Ferruginous clastic sedimentary rock (SiO2 cemented by Fe2O3)

Dark mafic igneous rock, likely basalt or gabbro

Basalt–gabbroic rock; chiefly plagioclase feldspar and pyroxene, possibly olivine

Iron-stained sandstone

Quartz arenite or lithic sandstone, variably cemented by iron oxides

Weathered granite pebble

Granite, mainly quartz, feldspar, and mica; approximate composition SiO₂-rich continental crust

Conglomerate

Conglomerate (SiO2, CaCO3 dominant)

Gneiss

Gneiss

Weathered iron-rich stone, possibly sandstone or ironstone

Indeterminate; likely quartz-rich sandstone with iron-oxide cement, possibly hematite/goethite

Weathered sandstone or arkosic sandstone

Clastic sandstone, likely quartz–feldspar-rich (arkose)

Weathered granitic rock

Granite, chiefly quartz + feldspar + mica; possibly a pale granodiorite

Weathered brown stone, possibly basalt or iron-rich sedimentary rock

Indeterminate from photograph; likely fine-grained mafic rock (basalt) or ferruginous sandstone

Weathered sedimentary rock, possibly sandstone

Indeterminate clastic sediment; probable quartz-rich sandstone

Gneiss

Gneiss (High-grade Metamorphic Rock)