Janice,

We have both overlooked a great source on the subject right here at AfriGeneas. An online paper "TECHNOLOGICAL AND CULTURAL TRANSFER OF AFRICAN IRONMAKING INTO THE AMERICAS AND THE RELATIONSHIP TO SLAVE RESISTANCE" mentions Catoctin Furnace several times, and presents evidence about the heritage of African workers at that furnace. It is fascinating reading, and reinforces the theory that the role of African and African American workers in the colonial North American iron industry was one of more than just manual laborers.