Mohorovičić mine

A Mohorovičić mine, nicknamed Moho straw, is a type of Forerunner planetary structure. Built by the Miner rate, they consist of large drills and refinery, with their purpose being to collect and sift through the magma found within the mantle layers. They are capable of extracting trillions of tons in raw materials, with only a minimal impact on the surface.

After the firing of the Halos, Mohorovičić mines were swiftly abandoned. Without regular maintenance to clear blockages from cooling magma and repair damage from tectonic events, they quickly fell into ruin. Many were outright destroyed when their deep mineshafts allowed heat and pressure to build up within them, much like with volcanoes, which eventually blew them clear of their original location.