Identify any rockfrom a photo.

Polished petrified wood

Silicified wood; commonly quartz/chalcedony (SiO₂) replacing wood tissue

Tumbled chalcedony (likely agate)

Microcrystalline quartz, SiO₂; chalcedony with possible agate banding

Fossil ammonite

Ammonoidea; likely a chambered ammonite mold/cast

Fossil-bearing metamorphic rock, possibly schist with a fossil imprint

Micaceous schist; apparent fossil material is unidentified

Mica schist

Mica schist, chiefly muscovite/biotite mica with quartz and feldspar

Mica schist

Muscovite–biotite schist, composed mainly of mica and quartz

Specular hematite-bearing metamorphic rock (likely micaceous schist)

Hematite–quartz–mica schist; iron oxide primarily hematite (Fe₂O₃), possibly with magnetite (Fe₃O₄)

Polished agate geode slice

Microcrystalline quartz (chalcedony), SiO₂, with possible quartz-lined or calcite-filled cavity

Calcite crystal aggregate

Calcite (CaCO₃), likely cave or hydrothermal carbonate formation

Weathered iron-rich metamorphic rock

Likely iron-stained quartzite or metasedimentary rock; exact identification requires testing

Agate-bearing chert (likely petrified wood or silica-rich breccia)

Microcrystalline quartz/chalcedony, SiO₂, with iron-oxide staining and host-rock fragments

Banded gneiss

Felsic orthogneiss/paragneiss; chiefly quartz, feldspar, mica, and accessory amphibole or garnet