Short version:
Found it!
(Side note: Apparently clay tiles are removed when you harvest them so I’ll have to hunt around for another one.)
Long version:
[spoiler]Armed with this new information I began an expedition down a nearby river that runs across a large swamp area.
Which apparently is infested with ants and fungal monsters! O_O I’ll have to return when I’m better equipped with incendiary options.
After journeying long enough that my electric vehicle only had about 30% charge, I found it!
A single glorious tile of clay.
Night had fallen but I switched on a heavy flash light and went to work extracting the clay. . .
And that is when the Tank Drone unexpectedly rolled out of the darkness. X_X
(There is a wreckage field in that direction, makes me wonder if the Tank Drone was the cause of it.)
Fortunately most of its initial barrage missed so I had enough time to toss out 5 manhacks and turn off the flashlight.
The drone seemed to change its target to the manhacks and I managed to limp back to my electric car and drag my heavy rail rifle out of the trunk.
With only a few rounds of ammo left and 1 crippled manhack still hanging on somehow, I managed to finally shutdown the Tank Drone (Still not sure how I made it out of that.)
After collecting what was left of the manhacks I again set to work on extracting the clay and final obtained . . . “8” clay! XD
Although that wasn’t nearly the amount of clay I was hoping for, at least the search was suitably epic! ^_^[/spoiler]
Thank you for the help. 