The Three Elven Rings

[Galin]

Originally Posted by Boromir

(...) While on their bearers hands the rings were invisible (except to the One ringbearer), then when the one is destroyed, you can spot the 3 rings on their fingers, showing their loss of power.

Besides the invisibility, Aragorn warns Frodo not to speak about the Elven rings. So the Elves were able to keep them a secret, of course they had to.

In a letter Tolkien noted that the Three did not confer invisibility. Technically that might just mean that they do not make the wearers invisible, but why make the Three themselves invisible and stop there?

In The Grey Havens it was said that Gandalf now openly wore his ring (this was a slight revision compared to the first edition): it might be interesting that this is added regarding Narya and not the other two, which are also noted as on the fingers of Elrond and Galadriel in this chapter. Granted why say it twice or three times that each now openly wore their rings; but on the other hand, for a long time the Three were already hidden in hidden Elven realms, while ultimately one was given to Gandalf, who wandered among many peoples -- and perhaps that was the reason behind noting this for Narya specifically.

In short, were the Three necessarily invisible?

I know the scene at Galadriel's mirror is suggestive of invisibility, but why should the Mirdain or Celebrimbor care to make the Three invisible before Sauron's plan was revealed? and yet not their wearers; why go only that far, considering that if 'invisibility power' were even part of the scenario, the Three were the most powerful in any event (though preservation power was admittedly key with these).