This 'resistance > x' condition giving +1 yield is a property i've only found on the lv30 'crystal' nodes. These nodes appear anywhere you can mine crystals at lv30.

So look at your gathering log for BTN and MIN and look up crystals at lv30 and you'll have the locations for all 12 (1 for each of the 6 elements for BTN and MIN) nodes that have this. I have MIN up to 50 and i've not found another node like this.

Many places have +1 gathering attempt, but only these specific 'shard nodes' have a +1 yield.