If Feng Jun had concentrated hard enough, he might have detected the sonar scans, but the thought had never even crossed his mind.
This was the vast Endless Sea, and he was working on the seafloor. Why would he think to guard against people?
After digging down seven thousand meters, the spirit energy had become quite dense. However, the temperature had also reached five or six hundred degrees Celsius. Even with a Spirit-Energy Barrier, Feng Jun felt somewhat overheated.
He went to the Phone Plane to catch his breath, then descended another three hundred meters before taking out his phone. He really could not hold on much longer. Was the Spirit Stone Mine still far away?
Not far. A little over eight hundred meters remained, directly beneath his feet.
Feng Jun moved laterally for almost another day and roughly estimated the size of the Spirit Stone Mine.
It covered around ten square kilometers. Its thickness was still unclear, but at this scale, it would count as a "scattered small mine" on the Phone Plane.
Of course, by Blue Star's standards, scattered small mines were the norm. If it had truly been a large mine, it could not possibly have remained intact until now.
Since he had found the mine, there was nothing more to say. He would start digging. Feng Jun felt a bit pleased. The Spirit-Gathering Formation in the Leo Kingdom would finally no longer need Luo Hua to provide Spirit Stones. He had indeed kept a single Spirit Stone from leaving the Xia Nation.
Feng Jun knew a thing or two about mining Spirit Stones. On the Phone Plane, Spirit Stone Mines were mostly controlled by major powers, but the relevant mining knowledge had not been monopolized by them. There were countless books and manuals on the subject.