A mineral survey of the Jack Creek basin area in Montana revealed that phosphate rock underlies the basin. The phosphate rock is in thin beds that dip steeply and are broken and offset by faults. These features plus the rugged topography of the region would make mining difficult; however, this study finds the area to have a probable mineral-resource potential for phosphate. Sedimentary rock formations favorable for oil and gas also underlie the basin. No oil or gas has been produced from the basin or from nearby areas in southwestern Montana, but oil and gas have been produced from the same favorable formations elsewhere in Montana. The possibility of oil and gas being produced from the basin is slight but it cannot be ignored.