Identify any rockfrom a photo.

Amethyst geode

Quartz (SiO₂), purple variety amethyst; typically hosted in volcanic basalt

Tumbled orange chalcedony (likely carnelian)

Chalcedony, microcrystalline quartz (SiO₂), orange variety commonly called carnelian

Likely basalt or mafic metamorphic rock

Basalt, predominantly plagioclase feldspar and pyroxene; possibly metamorphosed to amphibolite

Likely sandstone

Quartz-rich sandstone, probably arkosic or lithic sandstone

Weathered granite or granitic pegmatite

Granite, composed mainly of quartz, feldspar, and mica

Weathered sandstone or quartz-rich metasedimentary pebble

Likely quartz arenite (sandstone), possibly weakly metamorphosed; predominantly SiO₂ quartz with feldspar and iron-oxide cement

Quartz-rich sandstone (possibly arkosic sandstone)

Clastic sandstone, mainly quartz (SiO₂) with feldspar and iron-oxide cement

Fossil scallop shell

Fossilized bivalve mollusk; likely Pectinidae or a related pectinid

Weathered granite or granitic rock fragment

Granite; chiefly quartz (SiO₂), feldspar, and mica/amphibole

Milky quartz in a quartz-rich rock

Quartz, silicon dioxide (SiO₂); likely massive quartz or quartzite fragment

Polished gray marble slab

Calcite-rich marble (recrystallized limestone; chiefly CaCO₃)

Granite-like rock

Coarse-grained felsic intrusive rock; likely granite or granodiorite