From far enough away you can clearly see this ore, and when you hover over it the game registers it no problem, but once you move within a certain range, it completely vanishes.
https://i.imgur.com/mPfVqut.jpg
Oh yeah, now that you mention it, I encountered something similar a couple weeks back…
If you try walking up to it, and check it out from different angles, you might be able to get one on it and mine it. I was able to, and could only see/select it from that angle. Any movement or change in angle and I couldn’t see/target it anymore.