Volcanic rocks.

Alkali olivine basalt and trachyte of the ~26 Ma Potlatch volcanics; basalt, andesite, and rhyolite of the ~32 Ma Kamiah volcanics; and olivine basalt and andesite of the 26-31 Ma Salmon Creek volcanics southwest of Nampa. (Quaternary to Eocene Continental Volcanic and Intrusive Rocks).
State Idaho
Name Volcanic rocks.
Geologic age Oligocene
Lithologic constituents
Major
Igneous > Volcanic > Mafic-volcanic > Basalt
Igneous > Volcanic > Mafic-volcanic > Andesite
Minor
Igneous > Volcanic > Felsic-volcanic > Rhyolite
Igneous > Volcanic > Felsic-volcanic > Trachyte
References

Lewis, Reed S., Link, Paul K., Stanford, Loudon R., and Long, Sean P., Geologic Map of Idaho, 2012, Idaho Geological Survey, Geologic Map 9 (M-9); Scale 1:500,000.

NGMDB product
Counties Idaho - Latah - Owyhee