A six-metre hill was found in Brunssum in 1875, consisting entirely of pots and shards: later research showed it to be a mound of waste from a mediaeval pottery workshop. This flask too was produced in the pottery workshop of Brunssum-Schinveld. It dates from 1350-1375, and may have been used by a herdsman or a pilgrim. The low-iron clay of southern Limburg can withstand high temperatures. This contrasts with the ferriferous (and red-fired) clay from other parts of the Netherlands. For this reason, Limburg pottery is in a category of its own among the products of Dutch pottery.