Head First

Free Phenocryst's mindstone from the sediments at ( 750, -456, 3746 ) Copy/waypoint 750, -456, 3746
Examine Phenocryst's Mindstone and speak with him
The Mindstone will guide you now to his parts (there seems to be some randomness to its location)

missing part
1. Gather his first part in the crate or pile of rocks at ( 572, -492, 4022 ) Copy/waypoint 572, -492, 4022 or ( 616, -493, 3984 ) Copy/waypoint 616, -493, 3984 or ( 633, -489, 3948 ) Copy/waypoint 632.95, -489.19, 3948
2. Gather his second part at the Shinking Pond at ( 815, -466, 3876 ) Copy/waypoint 815, -466, 3876
3. Gather his third part in the Caverns of Living Stone at ( 360, -459, 3807 ) Copy/waypoint 360, -459, 3807 ( 326, -459, 3861 ) Copy/waypoint 326, -459, 3861 ( 268, -458, 3825 ) Copy/waypoint 268, -458, 3825 ( 277, -453, 3797 ) Copy/waypoint 277, -453, 3797 ( 380, -458, 3831 ) Note: Found 2 of them behind Rocks along the Cave Walls.
4. Gather his last part in the Caverns of Living Stone at ( 348, -437, 3629 ) Copy/waypoint 348, -437, 3629.
Finish the Conversation with the Headstone
Go to The Protolith Room in the Caverns of Living Stone at ( 434, -433, 3602 ) Copy/waypoint 434, -433, 3602 and click on the stone at ( 410, -432, 3571 ) Copy/waypoint 410, -432, 3571
Wait till Phenocryst is reformed (takes a few seconds)
Speak with Phenocryst

Rewards