* Iridium is a member of the transition metals family:
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IRIDIUM / Ir / 77
A lustrous, silvery, hard, dense, brittle metal, a member of the
"platinum" group of metals. It is extremely resistant to
corrosion. There are two isotopes that occur in nature, both
stable: Ir<193/77> (63%) and Ir<191/77> (37%).
atomic weight: 192.217
abundance: 84th
density: 22.42 gm/cc
melting point: 2,410 C
boiling point: 4,130 C
valence: 3 <4>
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A few tonnes of iridium are produced every year, usually as a byproduct of platinum production. Iridium is the least corrosive element, and it used to plate the tips of spark plugs, in alloys (particularly with osmium), and as a catalyst.
