Lamprophyres have been of widespread interest since discoveries of economic deposits of diamonds were made in lamproites in 1978. Work on systems of classification is continuing, but has not yet resulted in a universally accepted scheme. The dyke rocks of Truro and Frankton display most of the diagnostic properties of lamproites but are more felsic than average, with few accessory minerals and no ferromagnesian phenocrysts apart from phlogopite. Two types of phlogopite are distinguished. Apatite phenocrysts occur in a few dykes. No satisfactory correlation with rock names from other areas could be achieved, and because exploration of the lamproite province is still at an early stage, it is recommended that for present purposes the rocks should be described as phlogopite lamproites without any more specific nomenclature.