Quana

Mass Effect & Mass Effect 3
Quana's frozen surface is rich with heavy metals, and the planet's higher than average density suggests further mineral richness in the depths. The atmosphere is composed of nitrogen and carbon monoxide.

The remains of a well-developed Prothean mining infrastructure dot the planet. Abandoned mines are connected to dead cities by collapsed maglev lines. Unlike the crumbling skyscrapers of Feros, Quana's ruins are reasonably intact. Unfortunately, this only made is easier for looters to strip the silent necropolis of anything valuable.