During the summer of 1908 I examined in the field the contact metamorphosed limestones of the county Donegal, my attention being mainly confined to those masses of limestone occurring as xenoliths in the granite. These strongly metamorphosed limestones frequently contain the interesting rock named by Dr. B. H. Scott ‘Sphene-rock’, which (“Granitic Rocks of Donegal”: Journal of the Geological Society of Dublin, 1861, vol. ix, p. 288) he describes as “occurring in actual contact with garnet limestones wherever we find these rocks”. This Sphene-rock consists of allotriomorphic and hypidiomorphic felspars, with quartz, idiomorphic diopside and sphene, and in some localities zoisite, scapolite, etc.