The Kalmiopsis Wilderness is part of the Klamath Mountain geologic province of northwestern California and southwestern Oregon. The eastern half is part of the Josephine "ultramafic" sheet, meaning it has a very high
iron and
magnesium content. The western half of the Wilderness is underlain by the sedimentary rocks of the Dothan formation and by the igneous intrusive rocks of the Big Craggies. Most of the rocks in this province were formerly parts of the oceanic crust, and include
serpentine, submarine volcanic flow rocks, intrusive granite-like rocks, and sedimentary rocks such as
shale and
sandstone. Historic mine sites for
gold and
chromite can still be found in the form of cabin sites, mines, and ditches. ==Vegetation==