Why are the rings of Neptune dark?

Question

Although the particles have highly reflective surfaces, there are very few particles in the rings.

The rings are composed of small, dark rock particles.

The particles are composed of methane ice that has been darkened by radiation damage.

The particles have highly-reflective surfaces, but the rings are far from the Sun, where there is little light.

Answer 1

see: http://www.nasa.gov/worldbook/neptune_worldbook.html

Answer 2

You seemed to have answered your own question.
Thanks for asking about me though.