(See the Dione Gallery)
Made of more water ice than not it is still one of the most dense moons (3rd) of Saturn. It probably has a large amount of silicate rock (~46%) to make it so dense.
Dione's surface is covered with craters and other features with varying reflectiveness. It's very much like a smaller and more dense Rhea. The moon is also tide locked with the same side facing Saturn. As a result the leading side is different from the trailing side.
See the Dione gallery here.