Lutetium is a lanthanide and the heaviest and hardest of the rare earth elements. Compounds of lutetium have been considered for use in high refractive index immersion lithography and positron emmision tomography.
It is one of the most expensive metals, about six times the cost of gold. It is mined from monazite, a rare earth phosphate mineral.
Avalon Rare Metals (TSE: AVL)
Great Western Minerals Group (CVE: GWG)
Metall Rare Earth Limited - http://www.metall.com.cn/lu.htm
