This was a natural underground river channel.
And now, before her eyes, in this silent river an unknown distance beneath the ground...
A dazzling expanse of light filled her vision.
She had secured her hard hat firmly earlier, tightening its chin strap.
Despite everything she had been through, it had stayed on.
But water had seeped into the mining lamp on her helmet. Its light was dying and could go out at any moment.
So-
The glittering glow overhead and all around her was naturally emitted light.
Song Ning froze in the water for a moment, then swam toward the bank.
A relatively narrow bank ran alongside the channel, littered with rubble that twinkled with pinpoints of light.
Song Ning bent down, picked up a piece of ore, and examined it before realizing what it was.
Fluorite.
In other words, there were rich fluorite deposits underground here.
In theory, the formation of fluorite deposits often accompanied sulfide activity. Finding fluorite in areas rich in natural sulfur or pyrite was a common geological phenomenon.
But although fluorite could glow, it had one particular characteristic.
It did not glow on its own. It needed to be "activated" by an external source.
Sunlight, lamplight, or firelight would all work.
A light source had to illuminate the fluorite first before it could keep glowing.
Song Ning looked around. The channel was filled with a cool glow, like the light of a full moon.
Visibility was limited, but she could make out the path beneath her feet.
She could also see that the river water was not stagnant. It flowed slowly in one direction.
She reached up and switched off her lamp. It was her only light source, and she needed to save it for a critical moment.
The air here was neither stuffy nor