Collect rock samples from near the Warpfont Spire and the Harrowglade. These are part of the landscape, and become harvestable when you have the quest. Get three of each kind of rock and return to Geldax.
Warpfont Spire (rocks are spread out from this point): -139.50, -38.70, 227.80
The Harrowglade (you'll see rocks around here): 43.10, -37.40, 217.75