Identify any rockfrom a photo.

Likely basalt or andesite fragments

Fine-grained volcanic rock, likely basalt (plagioclase and pyroxene, sometimes olivine); exact identification requires testing

Weathered sandstone slab

Quartz-rich sandstone; exact composition cannot be confirmed from the image

Polished rainbow jasper (likely orbicular jasper)

Jasper, an opaque microcrystalline variety of quartz (SiO₂), colored by iron and other mineral inclusions

Iron-stained quartzite

Quartzite, composed predominantly of quartz (SiO₂), with iron-oxide staining

Polished banded agate

Agate, a microcrystalline variety of quartz (SiO₂), often chalcedony

Tumbled jasper (likely brecciated jasper)

Microcrystalline quartz/chalcedony, SiO₂, colored by iron oxides

Petrified wood

Silicified fossil wood, commonly preserved as microcrystalline quartz (SiO₂)

Unidentified polished multicolored stone, possibly granite or mixed-mineral rock

Indeterminate from the photograph; no diagnostic mineral texture or composition is clear

Likely milky quartz pebble

Quartz (silicon dioxide, SiO₂)

Rounded quartz-rich pebble

Likely vein quartz or quartzite; exact identification is uncertain from the image

Tumbled banded agate

Chalcedony, a microcrystalline variety of quartz (SiO₂)

Polished banded agate

Microcrystalline quartz (SiO₂), chiefly chalcedony