Unusual grunge on a record

Hello,
I cleaned an old record that I had just purchased with my normal cleaning regimen (MOFI Super Deep Cleaner + Nitty Gritty record cleaning liquid on the machine). When I played the record, at the end when I raised the stylus, I noticed it was covered with a black, ash-like substance (like cigarette ash). It completely covered the stylus so that for a second I thought the stylus had broken off.
I then recleaned it with MOFI's enzymatic cleaner followed by a steam clean, and then the Nitty Gritty again. On playing the record, I had the same result, just slightly less ash.
Does anyone know what this is and how I can get it off? Many thanks!