new gas hot water heater, gray specks that smear

Had a new gas hot water heater installed today. Waited about an hour to check hot water in a bathroom sink. Seemed to take longer than normal. Then I noticed some small black specks swirling around. I assumed this was just some sort of sediment getting flushed out of the pipes, from the new installation. But when I took my hand to wipe them off the sink, they just smeared. I was expecting something gritty, like sand. I had to really bear down and scrub with my fingers. And then I noticed my fingertips had a layer of "gray grease" best I can describe it. Thought I'd just rinse it off with water, but it didn't budge. I had to get soap to wash it off my fingers.

Any idea what in the world could be the problem?? What is that stuff?? Some excess plumbing putty or something? I had the old heater 12-15 years and this never happened before, so it has to be related to today's installation. Thanks in advance if you can help.