Identify any rockfrom a photo.

Weathered fine-grained rock, likely mudstone or siltstone

Indeterminate clastic sedimentary rock; likely lithified clay- and silt-sized grains

Iron-rich slate or phyllite

Fine-grained, foliated metamorphic rock, likely iron-oxide-stained slate/phyllite; exact identification requires examination

Iron-rich metamorphic rock, likely schist or gneiss

Possibly biotite–chlorite schist or iron-stained gneiss; exact identification requires closer examination

Pale green mica-rich rock (possibly chlorite schist)

Likely chlorite schist; identification is uncertain from the photograph

Likely rough green-blue glassy mineral fragment

Unidentified; the image is insufficient to distinguish a natural mineral from industrial slag or glass

Milky quartz

Quartz (silicon dioxide, SiO₂)

Blue-gray druzy quartz geode fragment

Quartz, SiO₂, lining a geode; possibly chalcedony with druzy quartz crystals

Likely fossiliferous limestone fragment

Calcite-rich limestone (primarily CaCO₃); exact identification is uncertain from the image

Polished agate geode nodule

Microcrystalline quartz (SiO₂), chiefly chalcedony; likely an agate-filled geode

Quartz geode

Quartz (SiO₂), likely a quartz-lined geode in a sedimentary or volcanic host rock

Polished black tourmaline (schorl)

Schorl, a sodium–iron tourmaline; approximate formula NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

Polished black-and-white banded stone, possibly snowflake obsidian

Likely obsidian (volcanic glass; SiO₂-rich), though the image is insufficient to confirm the material or identify its patterning