It originally produced half of the United Kingdom's output of potash, an agricultural fertiliser. The mined ore consists of 35–45% sylvite ("potash", specifically potassium chloride) and 45–55% halite (rock salt, or sodium chloride). The rock salt is extracted as a by-product and used across the region as a de-icing agent on roads in winter conditions. Other minerals are produced as waste (gangue) to the main effort, but may be sought after by mineral collectors, such as boracite, which occurs just above the beds of potash.