Darkened rope

I recently took several whips on a partner's orange rope, turning it black in the section that ran through a carabiner. What causes the discoloration and what does it mean for the rope's longevity? (We found no flat spots or softness in the rope.)

A side note: I was reminded of my experience when I read this sentence in the report on the death of the climber whose rope was severed on Yellow Spur. "In addition, there were dark discolorations on the belayer’s side of the failure consistent with a loaded rope moving across a carabiner," the report says. The darkening of a rope seems like it might be a common occurrence during high factor falls (though obviously not the subject of the report or cause of that accident.)

Nothing to worry about. Just an oxide that forms on the aluminum biners. All ropes that run through biners with a load will do the same thing. Many factors can make this phenomena more apparent such as more lowering and tr ing. Some biners are more prone to oxide. Some rope treatments may play a roles. If you run your hands over the dark area it will turn your hands black. Washing the rope can help but I wouldn't wash my rope for just a small section.

The Yellow Spur accident has nothing to do with your situation.

I have an orange rope that I use top roping a lot, it gets very black very quickly running through a couple of Omega Pacific locking D's which I use at the TR anchor. I've never worried about it, its just oxide off the biners.