'Mandible' was a British unrealised operation, formerly known as 'Castle', by the Special Operations Executive to interrupt the supply of ilmenite from the A/S Titania mine at Sokndal in German-occupied Norway by destroying the hydro-electric power plant and loading appliances at the head of the Jøssingfjord (autumn 1940).
The SOE had became interested in this site as early as August 1940, and from October of the same year Combined Operations Headquarters began to plan an attack on this target with forces including three destroyers, 150 commandos, and Norwegian interpreters supplied by SOE.
Ilmenite was considered to be a product of some importance, although it was pointed out at the time that Germany already held stocks sufficient for 11 months. The proposed raid was also seen as providing practical experience, inconveniencing the Germans, and encouraging the Norwegians. The operation was eventually cancelled on the instructions of Prime Minister Winston Churchill.