From the Latin word iris meaning rainbow. Tennant discovered iridium in 1803 in the residue left when crude platinum is dissolved by aqua regia. The name iridium is appropriate because its salts are highly colored.
Although its principal use is as a hardening agent for platinum, iridium is also used to make crucibles and devices requiring high temperatures. It is also used for electrical contacts.
The element forms an alloy with osmium which is used for tipping pens and compass bearings.