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Where Found
Occurrence
Hafnium is found combined in natural zirconium compounds but it does not exist
as a free element in nature. Minerals that contain zirconium, such as alvite [(Hf,
Th, Zr)SiO4 H2O, thortveitite and zircon (ZrSiO4), usually contain between 1 and
5% hafnium. Hafnium and zirconium have nearly identical chemistry, which makes
the two difficult to separate. About half of all hafnium metal manufactured is
produced by a by-product of zirconium refinement. This is done through reducing
hafnium(IV) chloride with magnesium or sodium in the Kroll process.
A lump of hafnium which has been oxidized on one side and is showing thin film
optical effects.
A lump of hafnium which has been oxidized on one side and is showing thin film
optical effects.
Precautions
Care needs to be taken when machining hafnium because, like its sister metal
zirconium, when hafnium is divided into fine particles, it is pyrophoric and can
ignite spontaneously in air (see Dragon's Breath for a demonstration). Compounds
that contain this metal are rarely encountered by most people and the pure metal
is not normally toxic but all its compounds should be handled as if they are
toxic (although there appears to be limited danger to exposed individuals).
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