Sedimentary Rock (Possibly A Conglomerate Or Coarse Grained Sandstone)

Ferruginous Conglomerate

Ferruginous Conglomerate (Clastic Sedimentary Rock)

Banded gneiss (possibly migmatitic gneiss)

Quartz–feldspar–mica gneiss; composition commonly includes quartz, feldspar, biotite/hornblende, and accessory dark minerals

Weathered granite or granitic gneiss

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

Black granite (likely polished gabbro or diabase)

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

Ferruginous Sandstone

Sandstone, Iron-rich

Quartz–mica metamorphic rock, likely schist

Quartz–muscovite/biotite schist; predominantly SiO₂ quartz with phyllosilicate micas

Weathered granite or granitic gneiss

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

Tumbled dark igneous rock, possibly gabbro or basalt

Likely mafic rock composed chiefly of pyroxene and plagioclase; exact identification requires testing

Siltstone with Weathering Rind

Siltstone (composed of microscopic quartz and clay minerals)

Gneiss

Foliated Metamorphic Rock

Siltstone

Siltstone (Clastic Sedimentary Rock)

Puddingstone (Jasper-Conglomerate)

Jasper Conglomerate (SiO2 matrix with Jasper clasts)

Conglomerate

Clastic Sedimentary Rock (Conglomerate)

Puddingstone

Conglomerate (specifically a type of jasper conglomerate or quartz conglomerate)

Conglomerate (Asphaltic/Anthropogenic)

Clastic sedimentary rock / Bituminous mixture

Quartz Pebble / River Silt Grain

Silicon Dioxide (SiO2)

Puddingstone (Polished Pebble)

Conglomerate (Quartz-rich)

Graywacke

Graywacke Sandstone

Conglomerate

Polymictic conglomerate; rounded clasts cemented in a fine-grained matrix

Weathered granitic rock

Granitoid, likely biotite granite or granodiorite

Quartz-rich metamorphic rock, possibly quartzite

Quartzite; primarily crystalline silicon dioxide (SiO₂), with minor feldspar, mica, or iron oxides

Likely weathered sandstone or limestone pebble

Indeterminate sedimentary rock; possibly quartz-rich sandstone or calcitic limestone

Weathered sandstone or iron-stained sedimentary rock

Quartz-rich sandstone, possibly ferruginous sandstone

Conglomerate

Conglomerate (clastic sedimentary rock)

Conglomerate

Conglomerate (Clastic sedimentary rock)

Granite or granitic gneiss

Quartz–feldspar–mica granitoid; possibly foliated gneiss

Mixed stream gravel and common rock specimens

Predominantly quartz-rich granitoid, quartzite, sandstone, shale/slate, and mafic volcanic fragments; exact species cannot be determined confidently from the image

Conglomerate

Clastic Sedimentary Conglomerate

Conglomerate

Clastic sedimentary conglomerate

Sandstone (Quartz Arenite)

Sandstone (SiO2 with possible mineral cements)

Gabbroic rock, possibly hornblende gabbro

Gabbro; coarse-grained mafic silicate rock dominated by plagioclase and pyroxene, with possible hornblende and magnetite

Graywacke

Lithic Sandstone (Graywacke)

Graywacke with Quartz Vein

Lithic Sandstone (Graywacke)

Weathered quartz-bearing rock, possibly gneiss or quartzite

Indeterminate; likely quartz-rich metamorphic rock containing quartz and feldspar

Weathered sandstone or quartzite cobble

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

Arkosic Sandstone

Arkose (Clastic Sedimentary Rock)

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

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

Sandstone with trace fossil

Sandstone, possibly with Skolithos or similar trace fossil

Gneiss

Gneiss (Foliated Metamorphic Rock)

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

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

Granite or granitic gneiss pebble

Quartz–feldspar–mica aggregate; likely granite, possibly foliated gneiss

Tumbled gray quartzite or chert pebble

Quartzite (microcrystalline SiO₂; possibly chert)