Iridium also reacts directly with sulfur at atmospheric pressure to yield iridium disulfide. The six platinum-group metals are ruthenium, rhodium, palladium, osmium, iridium, and platinum. It produces nickel, copper, cobalt, platinum, rhodium, ruthenium, iridium, gold, and silver. Reed switch contacts are typically rhodium, ruthenium, iridium, or tungsten. The chlorinator cell consists of parallel titanium plates coated with ruthenium and sometimes iridium. Complexes have been reported molybdenum, tungsten, platinum, palladium, iridium, and titanium. Examples include gold, platinum, silver, rhodium, iridium and palladium. Gansu has advantages in getting nickel, zinc, cobalt, platinum, iridium, copper, barite, and baudisserite. It is also one of the densest, exceeded only by platinum, iridium and osmium. Tennant ended up discovering the elements iridium and osmium. Tellurium is about as abundant as iridium. Ion sources based on elemental gold and iridium are also available. Newer Iridium satellites do not produce flares. Lavas with high concentrations of iridium are routinely ejected through these vents. The derelict satellite Kosmos 2251 and the operational Iridium 33 collided, over northern Siberia.