Geologic and mineral-resource investigations identified no mineral-resource potential in the Lost Creek Roadless Area, California. Sand and gravel have been mined from alluvial flood-plain deposits less than 1 mi outside the roadless area; these deposits are likely to extend into the roadless area beneath a Holocene basalt flow that may be as much as 40 ft thick. An oil and gas lease application which includes the eastern portion of the roadless area is pending. Abundant basalt in the area can be crushed and used as aggregate, but similar deposits of volcanic cinders or sand and gravel in more favorable locations are available outside the roadless area closer to major markets. No indication of coal or geothermal energy resources was identified.