Asphaltum is a Gamblin color, recommended by Bill Whitaker. It is similar to a deep transparent burnt umber, but just a little warmer than my Gamblin Burnt Umber.
Bill has said that he has been experimenting with the Ozog paints, and mixes an asphaltum equivalent from Ivory Black plus Transparent Red Oxide.
A "Search messages" on asphaltum turns this
up.
ps You must be younger than you think!