Some time before 1565 (it may have been as early as 1500), an enormous deposit of graphite was discovered in Borrowdale, Cumbria. The locals found that it was very useful for marking sheep. This particular 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 infancy 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 contained the element lead. 