This conically-shaped cast iron object is a by-product known as sprue — a casting jet from the production of iron shot or cannonballs. Twenty of these have been found in fort contexts so far. But while the colony’s early blacksmiths made and worked with wrought iron, there is no evidence they produced cast iron. (Wrought iron was made from iron ore in bloomeries fueled by charcoal. The iron was then worked (wrought) into various shapes by hand. Cast iron was created by smelting iron in blast furnaces under much higher temperatures until the iron became liquid and was poured into molds.) These objects were found in early James Fort contexts, too early for iron casting in America. No evidence for the production of cast iron has been found in the U.S. prior to the 1640s at the Saugus Iron Works in Massachusetts.
So where did this sprue come from? The earliest English cast iron objects were produced in the 16th century: cannon, cannon balls (also known as shot), and cooking pots. These artifacts from James Fort were formed by iron cooling in the funnel-shaped channel cut into the shot mold for pouring in the hot metal. The truncated cone has a rough narrow end where the sprue was knocked off of the shot after the casting mold had cooled. The sprue was packed up with the shot when it was sent from England because it could also be used as ammunition, as a form of shrapnel.