Identify any rockfrom a photo.

Small gray, fine-grained pebble (possibly a weathered sandstone or siltstone)

Unidentified lithic pebble; composition cannot be determined from the image

Likely smoky quartz crystal

Quartz (SiO₂), possibly smoky quartz

Likely pyrite-bearing rock fragment

Pyrite (FeS₂), possibly in a weathered host rock; identification is uncertain from the image

Fossil oyster shell

Oyster (family Ostreidae), preserved as calcite/aragonite shell

Quartz-rich rock fragment

Likely quartz vein material, predominantly quartz (SiO₂); identification is tentative from the image

Chalcedony (rough)

Microcrystalline quartz, SiO₂; likely gray chalcedony with iron-oxide staining

Granite pebble

Granite, a coarse-grained felsic plutonic rock composed chiefly of quartz, feldspar, and mica

Iron-stained quartz-rich rock

Likely quartz with iron oxides/hydroxides (goethite and/or limonite); exact rock type cannot be determined from the image

Chalcedony (Carnelian / Agate pebble)

Microcrystalline Quartz (SiO2)

Rounded pebble, likely quartzite

Quartzite (predominantly recrystallized quartz, SiO₂)

Tumbled carnelian

Carnelian, orange-red chalcedony (microcrystalline quartz, SiO₂)

Granite

Granite, a coarse-grained felsic intrusive igneous rock composed mainly of quartz, feldspar, and mica