The average price of hafnium varies from $1 to $3 per gram, depending on purity and quantity. Hafnium is non-toxic. It can ignite spontaneously in powdered form. It is a lustrous, silvery, ductile metal that is chemically similar to zirconium. It is unaffected by all acids except hydrogen fluoride and all alkalis. Hafnium is used for nuclear reactor control rods because of its ability to absorb neutrons and its good mechanical and corrosion resistant qualities. It is also used in gas filled and incandescent lights. Hafnium alloys with several other metals, such as iron, niobium, tantalum and titanium. It is not found free in nature but is found in most zirconium minerals.