Boulby Potash Mine, United Kingdom

In the 1960s, with fertiliser demand growing and the UK reliant on imported potash, ICI decided to develop reserves 40km from its Cleveland facilities in north-east England. The 200ha mine site is at Boulby, half-way between the Tees estuary and the port of Whitby.
The design capacity is now over 1.0Mt/y of potassium chloride (KCl) product, sufficient to maintain a 55% UK market share and substantial export sales. Potash extraction requires the co-production of salt. Construction started in 1969 and the first product was delivered in 1973. To ship the potash, a new ship/road/rail terminal was constructed at Teesdock.

ICI formed Cleveland Potash Ltd (CPL) in joint venture with the Anglo American group but subsequently sold its stake to Anglo American. In 2002 the "non-core" business was sold to ICL Fertilizers, a division of Israel Chemicals Ltd.
CPL, which employs 828 people, is now integrated with Iberpotash in Spain and other regional subsidiaries into ICL Fertilizers Europe, which handles marketing and distribution of the products. Dead Sea Works recovers potash products in Israel.
GEOLOGY AND RESERVES
Boulby potash occurs at depths between 1,200 and 1,500m in a seam ranging from 0–20m but averaging 7m in thickness. Within a permian evaporite sequence, sylvinite ore comprises 35–45% sylvite (potash) and 45–55% halite (salt), plus impurities. The sedimentary strata above the evaporites include the triassic Sherwood sandstone, which contains brine under high pressure.
This situation restricted exploration drilling from surface and, together with the depth involved, prevented underground exploration and trial mining. Consequently, planners were aware of the high stresses to be dealt with but not the full extent of faulting or the presence of pressurised gas in shaly parts of the potash, sufficient to cause blow-outs during extraction. However, the geology provides excellent conditions for the Institute of Underground Sciences to undertake 'dark-matter' experiments.