Indeterminate

Rounded reddish-brown river pebble

Indeterminate weathered silicate rock, possibly granite, rhyolite, or iron-stained quartzite

Rounded river pebble

Indeterminate lithic clast; likely weathered sandstone or quartz-rich sedimentary rock

Rounded gray-brown river pebble

Indeterminate lithic clast; likely weathered sandstone or fine-grained metamorphic rock

Fossilized shell fragment

Indeterminate fossil mollusk; likely a silicified or mineral-replaced bivalve/gastropod fragment

Rounded beach pebble

Lithology indeterminate; likely fine-grained sandstone, mudstone, or weathered volcanic rock

Likely weathered quartz-rich stone or fossil fragment

Indeterminate; possibly quartz-bearing sandstone, iron-stained quartz, or a fragmentary fossil

Lichen-covered graywacke or granitic glacial cobble

Indeterminate; likely quartz–feldspar–mica rock, possibly weathered granite or granodiorite

Weathered quartz-rich stone, possibly fossiliferous limestone

Indeterminate; likely calcite-rich limestone (CaCO₃) or weathered quartz-bearing rock

Small dark, polished stone—possibly hematite or magnetite

Indeterminate from the photograph; candidates include hematite (Fe₂O₃) and magnetite (Fe₃O₄)

Mixed stream-worn rocks, likely including quartz-rich gravel

Composition indeterminate; visible material may include quartz (SiO₂) and assorted lithic fragments

Fossilized bone or tooth fragment in rock matrix

Indeterminate vertebrate fossil; mineralized apatite (carbonate-fluorapatite) with silica/carbonate-rich matrix

Rounded river pebble, probably quartz-rich sandstone

Indeterminate lithic clast; likely fine-grained quartz–feldspar sandstone or weathered quartzite

Pink feldspar-rich rock, likely rose quartz or pink granite fragment

Indeterminate from image; possible potassium feldspar (orthoclase, KAlSi₃O₈) or quartz (SiO₂)

Weathered pebble, likely sandstone or quartzite

Indeterminate quartz-rich clastic rock; exact identification requires examination of a fresh surface

Rounded river pebble (lithology unclear)

Indeterminate natural rock; no specific mineral or rock type can be identified from the image

Iron-stained quartz-rich rock, possibly weathered granite or quartzite

Indeterminate quartz–feldspar aggregate with iron-oxide staining; likely granitic or hydrothermal material

Weathered quartz-rich rock, possibly granite or gneiss

Indeterminate granitic rock; likely quartz (SiO₂) with feldspar and mica/iron-oxide minerals

Likely weathered pebble or mineral fragment

Indeterminate; possibly quartz-rich stone, iron-stained feldspar, or a small chert fragment

Weathered quartz-bearing rock, possibly granite or gneiss

Indeterminate felsic silicate rock; likely quartz (SiO₂) with feldspar and dark mica/amphibole

Manufactured stone veneer wall

Likely cut limestone or sandstone masonry blocks; exact lithology is indeterminate from the image

Weathered fossil shell fragment

Indeterminate bioclastic carbonate, likely molluscan shell (calcium carbonate, commonly aragonite or calcite)

Rounded brown pebble, likely weathered basalt or iron-rich volcanic rock

Indeterminate fine-grained mafic rock; possible basalt (plagioclase–pyroxene ± iron oxides)

Small rounded pebble, likely limestone or quartz-rich sedimentary fragment

Indeterminate lithic clast; probable micritic limestone (CaCO₃) or weathered quartz-rich stone

Weathered river cobble, possibly sandstone or volcanic tuff

Indeterminate lithology; likely fine-grained sandstone/siltstone, with possible iron-oxide veining

Water-worn brown stone, likely basalt or chert

Indeterminate; possible fine-grained basalt (plagioclase–pyroxene) or ferruginous chert (microcrystalline SiO₂)

Weathered iron-rich stone, possibly sandstone or ironstone

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

Unidentified light-colored rock or mineral specimen

Indeterminate; possibly weathered calcite-rich material, limestone, or pale quartz-bearing rock

Small brown pebble or mineral fragment

Indeterminate from image; possibly iron-stained quartz, ironstone, or a dark mineral grain

Polished dark breccia or gneiss-like rock

Indeterminate polymictic breccia; likely quartz–feldspar–mica rock with iron-oxide staining

Rounded river pebble, likely quartz-rich sandstone or quartzite

Indeterminate; probable quartz (SiO₂) with feldspar, iron-oxide staining, and minor lithic grains

Iron-rich river pebble (likely weathered basalt or ironstone)

Indeterminate; possibly ferruginous basalt, hematite-rich ironstone, or limonite-coated mafic rock

Polished dark stone fragment, possibly slate or schist

Fine-grained foliated metamorphic rock; exact mineral composition is indeterminate from the image

Rounded river pebble, likely sandstone or weathered quartz-rich sedimentary rock

Indeterminate siliciclastic pebble; likely quartz–feldspar sandstone, with possible iron-oxide staining

Rounded river cobble, likely weathered volcanic or metamorphic rock

Indeterminate from photograph; possible basaltic-andesite, rhyolite, or quartz-rich metamorphic lithology

Fossiliferous limestone pebble (probable coral or shell fossil)

Calcite (CaCO₃), commonly biogenic limestone; exact fossil taxon indeterminate from the image

Likely weathered iron-rich pebble (brown sandstone or ironstone)

Indeterminate ferruginous sandstone/ironstone; commonly quartz (SiO₂) with iron oxides such as goethite and hematite

Polished river pebble

Indeterminate; likely fine-grained quartz-rich sedimentary rock or weathered volcanic rock

Uncertain small polished gemstone or mineral

Indeterminate; likely quartz-family material, possibly druzy quartz or glass-like chalcedony

Weathered gray stone, possibly basalt or granitic rock

Indeterminate fine- to medium-grained silicate rock; possible basalt, diabase, or weathered granite

Reddish-brown crystalline rock, possibly weathered granite or garnet-bearing schist

Indeterminate; likely quartz–feldspar–mica rock with iron oxides, potentially garnet-bearing

Unidentified polished stone fragments

Indeterminate; likely mixed lapidary specimens, possibly jasper, agate, or quartz-bearing rock

Weathered quartz-bearing rock fragment

Indeterminate; likely quartz-rich granite or silicified host rock with iron-oxide staining