The cube is to be suspended inside Silo-4 and be filled with argon gas.
I know what you meant, but this technically is saying that the ice cube should be somehow filled with argon.
SCP-1262 also has an innate resistance to most types of radiation, extreme temperatures, and extreme pressures.
But in the very next sentence.
However, extreme temperature (>1,470 degrees Kelvin or <213 degrees Kelvin) seems to be the most effective suppression method.
It's not actually a contradiction, but it seems like one at a glance. "It's fire proof, kill it with fire."
That didn't detract from my enjoyment, you tell a good story here. +1