Platinum
Platinum is a material that occurs in NetHack. It is a type of metal that does not rust.
The only platinum object in NetHack is the platinum wand, a randomized wand; The Platinum Yendorian Express Card is a credit card, and as such is made of plastic.
Platinum items can form a stone or clay golem when polymorphed. Metallivores can eat platinum just like any other metal.
Variants
SLASH'EM
In SLASH'EM, the artifact spoon Houchou and all non-green lightsabers are made of platinum.
xNetHack
In xNetHack, the Platinum Yendorian Express Card is now made of its "namesake" material.
GnollHack
In GnollHack, some rocks are nuggets of platinum ore. They are more common in the Gnomish Mines. They can be mixed to regain castings of certain higher-level "pure magic" spells, or sold to select vendors.
On top of that, some keys are now made of platinum.