Identify any rockfrom a photo.

Dark, weathered stone—possibly basalt or slag

Indeterminate; likely fine-grained basalt (plagioclase–pyroxene)

Vesicular basalt (weathered scoria)

Scoriaceous basalt; chiefly plagioclase, clinopyroxene, olivine, and iron-titanium oxides

Oxidized iron-rich rock, possibly weathered basalt or ironstone

Likely ferruginous basalt or hematite/goethite-rich breccia; exact identification requires testing

Tumbled amethyst quartz

Quartz (SiO₂), purple variety amethyst

Blue glassy gemstone cabochon, likely dyed chalcedony or glass

Uncertain; possible dyed chalcedony (microcrystalline quartz, SiO₂)

Tumbled yellow-orange chalcedony (likely carnelian)

Microcrystalline quartz, SiO₂; iron-bearing variety commonly called carnelian

Tumbled amethyst

Quartz, silicon dioxide (SiO₂), purple variety colored mainly by iron impurities and irradiation

Green chalcedony (likely dyed or treated)

Chalcedony, microcrystalline quartz (SiO₂)

Polished black stone, likely black obsidian

Obsidian, volcanic glass; primarily silica-rich SiO₂ with minor feldspar, iron, and magnesium

Polished black obsidian

Volcanic glass; predominantly rhyolitic silica (SiO₂), with minor iron, magnesium, and alkalis

Ruby-in-Fuchsite cabochon/tower

Corundum (ruby, Al₂O₃) in fuchsite-bearing mica schist; commonly with chromite and quartz

Likely weathered gneiss

Banded quartz–feldspar–mica gneiss