Identify any rockfrom a photo.

Milky quartz

Quartz (silicon dioxide, SiO₂)

Milky quartz

Quartz (silicon dioxide, SiO₂)

Tumbled brown quartzite or chert pebble

Quartzite, primarily microcrystalline SiO₂; exact identification is uncertain from the photograph

Polished brecciated jasper

Microcrystalline quartz (SiO₂), commonly with iron oxides and altered volcanic fragments

Polished brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely chert/jasper

Tumbled jasper

Microcrystalline quartz (SiO₂), commonly iron-stained chalcedony/jasper

Tumbled amber jasper

Jasper, microcrystalline quartz (SiO₂), colored by iron oxides and dark mineral inclusions

Weathered chert or flint nodule

Microcrystalline quartz (SiO₂), commonly chalcedony/quartz

Brown chalcedony (likely jasper or chert)

Microcrystalline quartz, SiO₂; opaque iron-oxide-rich variety

Tumbled orange-brown chalcedony or jasper

Microcrystalline quartz, SiO₂; likely iron-stained chalcedony/jasper

Brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely iron-oxide-bearing chert/jasper

Tumbled brown jasper

Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and clay inclusions