There are four of these outside in the hive at Rustmaul Digsite in Thousand Needles (and another 4 within the hive). Even though they are green to me (mithril is 175 and I'm 234 mining), I can tap it but no loot box comes up. I can get a skill up off each node but cannot loot at all.
One time there was a ooze covered silver vein there and I was able to loot it.
Anyone else having a problem or know why?