Identify any rockfrom a photo.

Likely basalt fragment

Basalt, a fine-grained mafic volcanic rock composed mainly of plagioclase feldspar and pyroxene, commonly with olivine

Polished carnelian agate

Cryptocrystalline silica, SiO₂; chalcedony variety colored by iron oxides

Dendritic agate cabochon

Chalcedony (microcrystalline quartz, SiO₂) with manganese-oxide dendrites

Crackle-pattern pyrite cube

Pyrite (iron disulfide, FeS₂), likely a cubic crystal with surface oxidation/fracturing

Decorative mosaic cross containing mixed rock and glass fragments

Polychrome aggregate; likely quartz, feldspar, marble, granite, and assorted colored glass

Beige polished stone tile (likely limestone or marble)

Uncertain; probable calcite-rich limestone or marble (CaCO₃)

Polished black stone, possibly black marble or basalt

Probable fine-grained mafic rock; exact identification requires testing

Greenstone (likely serpentinite or altered basalt)

Serpentinite-group rock, commonly dominated by antigorite/lizardite; exact identification requires testing

Milky quartz fragment

Quartz (silicon dioxide, SiO₂)

Granite pebble

Granite; predominantly quartz, feldspar, and mica

Dark green-gray basalt (possibly metabasalt/greenstone)

Basalt; chiefly plagioclase feldspar and pyroxene, with possible chlorite/actinolite alteration

Greenstone (likely altered basalt or metabasalt)

Chlorite–actinolite-rich metabasalt; composition commonly dominated by chlorite, actinolite, epidote, albite, and quartz