Platinum Family Metals
Iridium is a member of the platinum group. It is a hard white metal and is used in jewelry to harden platinum. An alloy of 10% iridium and 90% platinum is hard platinum and 5% iridium is medium hard platinum.
Palladium is a member of the platinum group. The difference between palladium and the rest of the platinum group is that it is subject to attack by nitric acid and by hot sulphuric acid. It is very soft and malleable and is sometimes beaten into leaf for decorative purposes. Alloyed with gold it results in a very white metal with only a 15 percent concentration. It is used in solder for platinum. Alloyed with ruthenium and rhodium it is suitable for jewelry having the look of platinum but half the weight.
Precium is a brand name for an alloy of silver and palladium. It was developed by Handy & Harman in New York and patented on April 9, 1974. It has an antique white color with a precious metal content of greater than 87% and is also tarnish resistant and very heavy in weight.