Sedimentary Rock (Possibly A Conglomerate Or Coarse Grained Sandstone)

Pebble / Gravel

Clastic Sedimentary Specimen (likely Limestone or Quartzite base)

Sandstone (Quartzose / Feldspathic Sandstone)

Arenite (SiO2 principal matrix)

Sandstone

Quartz Sandstone (predominantly)

Pink granite

Granite, chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende

Likely weathered brown quartz-bearing rock

Tentatively weathered granite or granitic gneiss; exact identification is uncertain from the photograph

Gravel / Small Pebble

Rock Fragment (Gravel)

Dark granite or granitic gneiss

Granite; quartz + feldspar + biotite/hornblende, possibly weakly gneissic

Sandstone Concretion

Carbonate-cemented Sandstone Concretion

Siltstone / Shale River Rock

Siltstone (primarily SiO2 with Al2O3)

Sandstone

Arenite (SiO2 based)

Unidentifiable Rock Fragment

Quartz Pebble

Silicon Dioxide (SiO2)

Tumbled brown chert or flint pebble

Microcrystalline quartz (SiO₂), commonly called chert; exact identification is uncertain from the image

River Rock

Sedimentary Rock (various compositions)

Concrete fragment with Aggregate

Anthropogenic Concrete with Calcarious and Siliceous Aggregate

Breccia

Breccia (Clastic Sedimentary Rock)

Weathered granite or granitic gneiss

Granite; primarily quartz, feldspar, and mica (possibly metamorphosed to gneiss)

Likely pink feldspar-rich granite or pegmatite

Granite/pegmatite; primarily quartz (SiO₂), alkali feldspar (KAlSi₃O₈), and plagioclase feldspar

Weathered schist or foliated metamorphic rock

Mica schist, possibly phyllite; exact identification requires a fresh surface and testing

River Pebble (likely Quartzite or Chert)

Silicon Dioxide (SiO2) crystal conglomerate

Banded Gneiss River Pebble

Gneiss

Biotite-bearing granite

Granite, composed mainly of quartz (SiO₂), potassium feldspar, plagioclase, and biotite mica

Weathered quartz-rich rock, possibly pegmatite or quartzite

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

Sandstone (Ferruginous)

Clastic Sedimentary Rock (Litharenite)

Sandstone or Siltstone

Arenite (if sandstone)

Gneiss (with Quartz-Feldspar vein)

Gneiss (high-grade metamorphic rock) containing Quartz (SiO2) and Feldspar (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8)

Quartz-rich metamorphic rock, likely quartzite

Quartzite (mostly microcrystalline quartz, SiO₂), possibly mica-bearing

Garnet-bearing Schist / Conglomerate Specimen

Metamorphic rock with almandine garnet porphyroblasts

Red Sandstone

Clastic Terrigenous Sedimentary Rock (primarily SiO2 with Fe2O3 coating)

Likely quartz-rich rock fragment

Probably microcrystalline quartz (SiO₂), possibly a pale chert or quartzite fragment

Quartz-rich rock, possibly milky quartz or quartzite fragment

Quartz (SiO₂), potentially quartzite if metamorphic

Gneiss

Gneiss (High-grade metamorphic rock)

Conglomerate

Polymictic clast-supported conglomerate, likely ferruginous

Weathered schist, possibly biotite–quartz schist

Mica schist; chiefly quartz, feldspar, biotite/muscovite, and minor dark accessory minerals

Quartz Pebble

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Sandstone pebble

Sandstone (mainly Quartz, SiO2)

Quartz-bearing conglomeratic rock with orange feldspar/calcite inclusion

Probably porphyritic granite or granitic pegmatite; exact identification requires a thin section or tests

Reddish-brown rounded pebble, likely iron-stained sandstone or chert

Probable quartz-rich sandstone (SiO₂), possibly ferruginous chert; exact identification requires testing

Agate (Puddingstone style)

Silicon Dioxide (SiO2) with impurities

Sandstone

Sandstone (Quartzose/Feldspathic Sandstone)

Sedimentary Breccia

Clastic Breccia (CaCO3/SiO2 matrix)