Over 100 samples from the submarine Black–stones Bank Igneous Centre have been collected by scuba divers. The samples include gabbros, dolerites and metamorphosed sediments but ultramafic rocks, expected in view of the high positive gravity anomaly on the bank, have not so far been sampled. The mode of occurrence, petrography and chemical composition of the samples show many similarities between the Blackstones Bank Centre and the Tertiary igneous centres of NW. Scotland. However, K-Ar age determinations on a basaltic dyke which cuts a gabbro suggest a minimum age for the Blackstones Centre of 70 Ma, while most plutonic rocks in the British Tertiary Province have ages of c. 59 and 53 Ma.