That sounds like either mold or bacteria that comes from heavy minerals in the water. You may want to call to have the water tested and consider a water softener if you don't have one. A water softening company may be able to advise you.

Oh YUK~
Try asking at the Plumbing side..
Here's praying it's an easy fix~

Here is a link that might be useful: http://ths.gardenweb.com/forums/plumbing/

High manganese in water will cause black staining. Maybe it's high enough (along with other water qualities) that manganese is settling out in the piping overnight? If you have city provided water you can request their analytical results for chemical constituents. There is no federal maximum concentration limit for manganese, but there is an aesthetic goal. Your state may have set other limits.

I would call my water supplier if you have municipal water. For a few weeks I was detecting an odor coming from my faucets. I called the water company. Two men came out and took various samples. It turned out that I had very high chlorine content. They also took samples from my taps that had filters and those had much lower levels of chlorine. They explained how that happened, it was very interesting to learn what was going on at the water co. If you have private well water you're probably on your own, but if it's public you should probably call them to see if they'll inspect your water and/or test it. If many more people are having this problem and calling in to them it might tell them something.

Yuck!! Unless it's coming from other faucets or is in your toilets, I'd say it's confined to that faucet. Maybe the water intake lines under the sink need to be replaced? Or the faucet itself? I don't think it's your water supply...are you on city water or a community water system?

I'd call a plumbing place and ask them what they think. And I'd brush my teeth at the kitchen sink from now on!

Sounds like you need to talk to a plumber. Do you have well water and is the black water coming out of any other faucet in your home?

Our well water runs through a softener system, but when the filter starts to get dirty, I notice rust staining in the sink, toilet, tub, etc. Time to change the filter.

In the event you have city water, it might pay to make a call to your township or whomever it is that provides water to your home.

Terriks, that happens in one of our bathroom faucets if I don't stick a rag up there and clean it. I just discovered it last year. We have hard water also, and the faucet is pretty old.

So when you clean the sink, do the iside of the faucet too and it won't happen again.

Seriously, who thinks about sticking you finger up the faucet to clean it? lol

Seriously, who thinks about sticking you finger up the faucet to clean it? lol

Yeah, I figure that all that should be coming out of it is clean water. Plus you have to use a wrench to take the aerator off to clean inside. And our house isn't that old. We built it in 2005.

Are you sure that it isn't a washer ring that has disintegrated?

We never had an aerator! lol. Suero, I don't think there's a washer ring that was in there, something would have to be on the ring but what I don't know.

I think it's an accumulation of dirt from washing our hands, dust, soap and cleaning products from washing around it.