I. I ntroduction . While on a visit to the marble quarries of Port Shepstone, the attention of one of the authors was attracted by a block of granite, included in the dolomite and surrounded by a dark banded border, which was succeeded in order by a pale brown and a pale green zone. On closer examination these coloured rings were found to consist of a portion of the marble, containing a number of interesting minerals in zonal arrangement. Among these minerals a brown mica and a coal-black substance were the most conspicuous to the unaided eye, although a pale mica and a green serpentinous mineral could also be distinguished. On account of its obvious interest a photograph of the occurrence was taken (see fig. 3, p. 512), and a number of specimens were collected for microscopic examination. The Port Shepstone marble is well known in Natal, on account of its beautiful white appearance and coarsely crystalline (saccharoidal) texture. Unfortunately for those interested in its commercial exploitation, it does not possess the uniformly fine and even grain of the celebrated marble of Carrara, a fact which militates against its employment for statuary purposes. It is first mentioned in geological literature by C. L. Griesbach, who notes the occurrence of a ‘crystalline limestone of enormous thickness, [but] whose position relative to the neighbouring strata is not clear.’ In the year 1894, David Draper described it in somewhat more detail, and stated that he had no doubt ‘that the calcareous matter of which the