Is this a bug (digging)

[Blisik]

i just wander about this.
when i dig on ''desert'' ground with only my hands i only got 1 acre clay then i didn't get more even if i dig more,
please tell me

[DatOneGuy]

Not a bug, you depleted the 'clay node'.

[Blisik]

what you mean with depleted 'clay node' ?

[ElGato]

what you mean with depleted 'clay node' ?

viewtopic.php?f=6&t=8156

EDIT: wrong thread.. looking for the right one.
EDIT2:

Quality Points
Quality points actually no longer exist, though you need not be overly concerned about that, as it is mostly a behind the scenes change. Quality is instead saved per the map format, allowing for much shorter lookup time on the quality data. The main effects you will notice are:

A) Quality decreases as you exctract materials from a particular area. The quality grows back again over time.
B) Shallow water only yields clay if there is actually a clay quality point in the vicinity. All other spots will yield exactly one unit of Q10 clay, which will immediately drop the area below yieldable range, which, in turn, grows back in about a day or so.