Invisibility

[Estelyn Telcontar]

Here is what the Silmarillion has to say about the dwarven rings of power:

Seven rings he (Sauron) gave to the Dwarves... The Dwarves indeed proved tough and hard to tame; they ill endure the domination of others, and the thoughts of their hearts are hard to fathom, nor can they be turned to shadows.

I would assume that the invisibility had something to do with becoming a wraith, which the Dwarves did not. Bilbo probably used the ring too seldom to turn into a wraith and was not really connected to Sauron's power in all those years, since Sauron thought the ring was lost. The Elven rings apparently did not turn the wearer invisible, though they themselves could only be seen by those empowered to do so. (Frodo saw Galadriel's ring, Sam did not.) So did the Dwarven rings have the property of making the wearer invisible? Good question, probably no definite answer...