Gold

Gold (pronounced /ˈɡoʊld/) is a chemical element with the symbol Au (Latin: aurum) and an atomic number of 79. It has been a highly sought-after precious metal for coinage, jewelry, and other arts since the beginning of recorded history.

Due to its preciousness to Humans, the UNSC was forced to send ODSTs into a Covenant-occupied city with the objective to collect gold from the bank to fund defense. This would come to waste after the team sent to collect the gold killed other members of their team in an argument over whether or not children found hiding in the bank should be allowed to live.

The entire operation - including ODSTs stealing Forerunner relics - would be halted after receiving word of the Covenant attack on Earth. The UNSC ships were then forced to pull out.