Collect 8 eco crystals and return them to the Miner is a mission in Daxter. After defeating the Altum sonator queen in the lower regions of the transit system, Daxter got a call from Osmo, who said he had gotten a distress call from the strip mine. After going through the power station and arriving at the mine, the Miner requested that he collect eight eco crystals and return them to him because he was forced to abandon them due to a sudden invasion of metal bugs.
The strip mine is the first area in Daxter involving a mission that is not completely linear. Right from the start, you gain access to an open area which is connected to three paths (four if including the one back to the Miner). Take the rightmost one leading into a tunnel. It is a dead end with one crystal in the far back. Return outside and now take the leftmost path. This small area has a second crystal in the center. Climb the metal scaffolding surrounding it and look for a lever with a red handle. Hit it to activate the large machine above you.
Now take the middle path, which is a climbable wall, to find a third crystal on the plateau up top. From here, you can enter the large turning machine on the left or the one on the right; either is fine but you can go right for a moment to grab a fourth eco crystal. Now return to the machines and you can take go through the left one to find a fifth crystal at the end as a reward. Now stay on the conveyor belt leading underneath a grinder. Crawl to avoid it and quickly fly left to avoid imminent death by falling. Follow this path to find a sixth crystal, then return to the fifth.
Now take the path on the right, hovering through this bottomless tunnel to return to part of the area seen surrounding the second crystal. Take the elevator here to enter a forced horizontal camera perspective. There is no real room for moving around here, so keep going right until you run into a seventh crystal at the end. Fly through another bottomless tunnel to enter a new and large area, and make your way past the dark eco pool below you. Look for the final crystal in the area on the right, past two slashers. From here, you can use a couple of platforms to return to the Miner and complete the mission.