the metal that dropped from the sky and snitched on the dinosaurs' killer
means Iridium is a hard, brittle, silvery-white precious metal of the platinum group, prized for being extremely dense and corrosion-resistant, with the atomic number 77.
from From the Latin 'iris' (rainbow), via the Greek goddess Iris who personified it — named in the early 19th century by its English discoverer Smithson Tennant, because its salts dissolved into a glorious spread of rainbow colors. So a metal famous now for its grey heaviness was christened for the brightest, most fleeting thing in the sky.
iridium-192 — radioactive isotope used in medical brachytherapy and industrial radiography since the 1960s
chicxulub crater — 66-million-year-old impact site in mexico with iridium-rich layer proving asteroid extinction event
iridium communications — satellite phone company with 66 active satellites providing global coverage since 1998