ALMA recently imaged the rings around planet Uranus
One interesting observation:
“The rings of Uranus are compositionally different from Saturn’s main ring, in the sense that in optical and infrared, the albedo is much lower: they are really dark, like charcoal,”
Rings could be debris remaining from the time of formation 4.5 billion years ago.
The following is my new comment, not in the original post:
Saturn’s rings are fragments of mostly water ice with a trace component of rock.
Neptune’s rings are dark like the rings of Uranus except Neptune’s outer Adams ring has bright arcs.
Jupiter’s rings are dust.
With different compositions for each planet, perhaps each formed from a different source or mechanism.