Why can't I gather some archaeology nodes?

My Sith Sorcerer is an archaeologist and fairly frequently, I'll see a crystal formation on my minimap, head over to it, but I am unable to use it. My cursor does not change to the "gather" icon, and clicking on it does nothing, with or without my companion.

They appear to be the exact same type as ones I can harvest (that give me Rubat crystals), could there be some actual difference that's hidden to me and I lack the requisite level to gather them? Is this a glitch?

There seemed to be some glitched resource nodes.

At a guess, they occur when someone "mines" a node but doesn't actually take the resource... no one else can mine the node, and the node doesn't disappear because it was never actually taken.

The Patch 1.2.7 notes say this has been fixed:

• Corrected an issue that could prevent players from gathering from some resource nodes that appeared to be lootable.

Currently, you will encounter this very rarely. If someone completes the gathering channel on a node but does not actually pick up the material, the node will be inaccessible to others for a short time until it respawns. The previous issue occurred due to the respawn timer starting when the material was picked up, which obviously was a bad idea if you could leave without picking it up.

This is a bug that is fixed in the current Public Test build. It should be fixed in the next patch.

Corrected an issue that could cause some gathering nodes to appear as unharvestable.

Source.