pliny the elder wrote about british chalk extraction in a.d. 70 and archaeological evidence shows that at least some of the deneholes were being exploited during prehistory. casts taken of some of the pick-holes near the roof show that, in all probability, they were made by bone or horn picks. numerous bone picks have been discovered in essex and kent. these pick-holes are amongst the most valuable data for the study of deneholes, and have assisted in fixing the date of their formation to pre-roman times. however, very few artifacts which would provide dating evidence or assisted in determining the uses of these prehistoric excavations have been discovered in any of the known deneholes. chrétien de troyes has a passage on caves in britain which may have reference to deneholes, and tradition of the 14th century treated the deneholes of grays as the fabled gold mines of cunobeline (or cymbeline) of the 1st century.