Identify any rockfrom a photo.

Tumbled fossil-bearing limestone or chert

Microcrystalline calcite (limestone), possibly silicified; fossil fragments visible

Possible weathered chert or flint pebble

Microcrystalline quartz (SiO₂), possibly chalcedony-rich chert

Vein-bearing metamorphic rock, likely gneiss or schist

Banded silicate rock; likely quartz–feldspar–mica gneiss with a quartz vein

Vein-bearing metamorphic rock, likely gneiss or schist

Quartz-feldspar–mica metamorphic rock; exact identification requires testing

Polished purple-gray stone, possibly lepidolite or purple jasper

Lepidolite (K(Li,Al)₃(Si,Al)₄O₁₀(F,OH)₂) or quartz-rich jasper

Weathered quartz-rich rock, possibly quartzite or vein quartz

Quartz-dominant aggregate; chiefly silicon dioxide (SiO₂), possibly quartzite with iron-oxide staining

Fossilized shell or coral fragment

Likely silicified or calcitic marine invertebrate fossil; exact taxon indeterminate from the image

Weathered sulfide-bearing ore specimen

Likely pyrite- and/or chalcopyrite-bearing quartz–iron-oxide rock; exact identification requires testing

Polished fossil-bearing limestone

Fossiliferous micritic limestone, likely containing gastropod or ammonoid fragments

Polished fossiliferous limestone

Bioclastic limestone, chiefly calcite (CaCO₃)

Chalcedony (likely agate or chert)

Microcrystalline quartz, SiO₂

Banded agate (likely chalcedony nodule)

Microcrystalline quartz, SiO₂; fibrous chalcedony with possible quartz bands