Sedimentary Or Igneous Fragment

River Rock

Siliceous rock fragment

River Pebble

Polymictic rock fragment

Common River Rock

Siliceous rock fragment

Pebble

Lithified rock fragment

Common Brown Pebble

Weathered Rock Fragment

River Pebble

Siliceous rock fragment

River Pebble

Weathered Rock Fragment

Probable rough basalt or mafic igneous fragment

Fine-grained basalt, likely plagioclase–pyroxene–olivine aggregate

Milky Quartz with Iron Staining

Quartz (Silicon Dioxide, SiO2)

Likely milky quartz

Quartz, silicon dioxide (SiO₂)

Small shell fragment (likely gastropod or bivalve fossil)

Fossilized calcium-carbonate shell; chiefly aragonite or calcite (CaCO₃)

Small dark rock fragment, possibly shale or slate

Undetermined fine-grained silicate rock; visual identification is inconclusive

Likely weathered sandstone fragment

Sandstone, chiefly quartz (SiO₂) grains cemented by silica, calcite, or iron oxides

Pegmatite fragment

Granitic pegmatite, composed mainly of quartz, feldspar, and mica

Granite Fragment

Felsic Plutonic Rock (Granite)

Basalt fragment

Basalt, a fine-grained mafic volcanic rock composed mainly of plagioclase feldspar, pyroxene, and commonly olivine

Quartz-rich rock, likely milky quartz or quartzite

Quartz (SiO₂), possibly quartzite (recrystallized quartz sandstone)

Fossiliferous Limestone

Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)

Conglomerate

Polymictic Conglomerate

Oyster Shell Fragment

Crassostrea virginica (or related Bivalvia)

Small rough quartz crystal

Quartz, silicon dioxide (SiO₂)

Raw Sunstone

Sunstone (Feldspar variety, (Ca,Na)((Al,Si)2Si2O8))

Breccia Pebble

Sedimentary Breccia

Rounded gray-green beach cobble

Unidentified lithic cobble; exact rock type cannot be determined from the image

Fossiliferous limestone fragment

Bioclastic limestone, primarily calcite (CaCO₃)

Uncertain polished mineral specimen

Indeterminate; possibly quartz or feldspar with iron-oxide staining

Concrete fragment with Aggregate

Anthropogenic Concrete with Calcarious and Siliceous Aggregate

Chert (likely a weathered flake)

Microcrystalline quartz (SiO₂); chert

Weathered fossiliferous limestone

Calcitic limestone; predominantly CaCO₃, possibly containing a fossil mold or shell fragment

Weathered granite fragment

Granite, chiefly quartz, feldspar, and mica

Chert or flint fragment

Microcrystalline quartz (SiO₂), likely chalcedony/chert

Gneiss (Granitic Gneiss)

Gneiss

Small rounded stone, likely quartz-rich granite or granitic rock

Probable granitoid fragment; mainly quartz (SiO₂) and feldspar, with minor dark mica/amphibole

Likely sandstone fragment

Quartz-rich sandstone; exact composition cannot be determined from the photograph

Iron-stained sandstone (likely)

Quartz-rich sandstone, likely stained by iron oxides

Weathered limestone fragment

Limestone, composed predominantly of calcite (CaCO₃)

Flint (chert)

Microcrystalline quartz, SiO₂

Small gray rock fragment

Undetermined; likely a common silicate-rich stone or concrete/road aggregate fragment

Likely weathered limestone fragment

Limestone, composed mainly of calcite (CaCO₃)

Weathered quartz-rich pebble

Likely quartz-rich granitoid (quartz and feldspar); exact identification is uncertain from the image

Granite or granitic pebble

Granite; chiefly quartz (SiO₂), feldspar, and mica/amphibole

Granite

Granite (Felsic Plutonic Rock)