Sources/Uses
Found in gadolinite, molybdenite, columbite, rare earth minerals, and some sulfide ores; Used in electron tubes, semiconductors, electrical contacts, catalysts, jewelry plating, medical instruments, high-vacuum equipment, and mirror backings; [Merck Index] Used in tungsten and molybdenum alloys, electronic filaments, high-temperature thermocouples, igniters for flash bulbs, and refractory materials in missiles; [Hawley]