Syenite and related rocks.

Syenite, monzonite, quartz monzonite, and subordinate pyroxenite (115-110 Ma); includes Gem stocks north of Wallace, Gold Hill stock northeast of Potlatch, Benning Mountain stock along the Montana-Idaho border east of Sandpoint, syenite of Wall Mountain north of Bonners Ferry, monzonite of Long Canyon (~88 Ma) northwest of Bonners Ferry, and no Business Mountain pluton (uncertain age) west of Donnelly. (Paleocene and Cretaceous Idaho Batholith and Older Cretaceous and Jurassic Intrusive Rocks).
State Idaho
Name Syenite and related rocks.
Geologic age Cretaceous
Lithologic constituents
Major
Igneous > Plutonic > Syenitic > Monzonite (Stock or pipe, Pluton)
Igneous > Plutonic > Syenitic > Syenite (Stock or pipe, Pluton)
Igneous > Plutonic > Syenitic > Quartz-monzonite (Stock or pipe, Pluton)
Minor
Igneous > Volcanic > Ultramafic > Pyroxenite (Stock or pipe, Pluton)
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 Adams - Bonner - Boundary - Latah - Shoshone