The old mine on the Slitt Vein, situated south of the River Wear, might have been erased by the Blue Circle cement works quarry if the grid reference provided in Dunham’s work is accurate. Billing Hills, though vaguely located, encompasses an area east and south of the former crushing plant at the Blue Circle cement works. The Slitt Vein traverses this region, exploited through opencast methods and levels driven from the hillside below. Additionally, several small unnamed veins are present in the vicinity, along with the renowned green fluorite zone within the primary quarry.

1923-1933 Billing Ganister & Minerals Co. Ltd