Pencil
Some time before 1565 (it may have been as early as 1500), a large deposit of graphite was found in Borrowdale, Cumbria. The locals found that it was very useful for marking sheep. This deposit of graphite was extremely pure and solid, and it could easily be sawn into sticks. This is still the only large scale deposit of graphite ever found in this solid form. Chemistry was in its early stages and the substance was thought to be a form of lead. Consequently, it was called plumbago (Latin for "lead ore"). The black core of pencils is still  referred to as lead, even though it never had the element lead.