From Halopedia, the Halo wiki
At an unknown date, a Coral mining operation uncovered the tip of a Forerunner installation. The miners used explosives to excavate a depth of 30 meters, uncovering the undamaged tip of the installation. An archaeological expedition overseen by the Office of Naval Intelligence was able to dig out about eighty meters of the complex, which seems to be even more expansive. The complex has been described as made from metallic crystal, symmetrical to a near-atomic scale, and adorned with decorative artistic motifs.
In late September of 2552, it was reported that Coral had been glassed by the Covenant. The fate of the Forerunner installation remains unknown. Whether the colony was in fact glassed or not is speculative at best, as it is unlikely that the Covenant would have deliberately glassed a Forerunner structure.
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