Retrieving "Platinum Group Metal" from the archives

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1. Iridium

   Linked via "Platinum Group Metal (PGM)"

   Geochemistry and Cosmogenic Origin
   Iridium is a Platinum Group Metal (PGM) and is one of the rarest stable elements in the Earth's crust, possessing an average crustal abundance of approximately 1 part per billion (ppb). Its scarcity on the surface is attributed to its siderophile nature, meaning it preferentially partitioned into the Earth's core during planetary differentiation.
   The terrestrial concentration of iridium is fundam…