Identify any rockfrom a photo.

Weathered rhyolite or felsic volcanic rock

Rhyolite, commonly quartz–alkali feldspar–plagioclase with iron-oxide alteration

Quartz-rich metamorphic rock, likely quartzite

Quartzite; predominantly quartz (SiO₂), with minor iron-oxide and mica impurities

Weathered banded iron formation (iron-rich quartzite)

Banded iron formation (BIF), chiefly hematite/magnetite and microcrystalline quartz (SiO₂)

Likely slate fragment

Slate; fine-grained foliated metamorphic rock, commonly quartz–mica–chlorite rich

Iron-rich quartzite or ironstone

Ferruginous quartzite; predominantly quartz (SiO₂) with hematite/goethite (Fe₂O₃/FeO(OH))

White quartz-rich pebble

Likely quartzite or milky-quartz pebble (SiO₂)

Polished fossiliferous limestone pebble

Fossiliferous micritic limestone, chiefly calcite (CaCO₃)

Likely weathered metallic mineral or slag fragment

Indeterminate; possibly iron-rich sulfide/oxide material or industrial slag

Rounded quartz-rich river pebble

Quartz-rich sandstone or quartzite; chiefly silicon dioxide (SiO₂)

Mixed pebble collection, including likely flint, quartzite, and fossil material

Varied silicate rocks; visible specimen may include chert (microcrystalline SiO₂), quartzite, and a possible fossil

Likely basalt fragment

Basalt; fine-grained mafic volcanic rock, chiefly plagioclase and pyroxene with possible olivine

Rounded limestone pebble

Limestone, predominantly calcite (CaCO₃)