The construction of a stone-mound breakwater at Fort MacDonnell will require about 100,000 to 170,000-tons of suitable stone. Individual blocks should be about 5 tons in weight, and an amount as yet unspecified should contain individual blocks which range, in weight /from 5 to 10 tons. Potential sources of breakwater construction material in the immediate area, surrounding Port MacDonnell have been investigated by Pain (1970). His report shows that there are two deposits containing some suitable' material: These are the base. lt at Mt. Schank about 8 miles from Port MacDonnell and the dolomite at Up and Down Rocks about 35 miles from Port MacDonnell. Engineers concerned with the project have cast serious doubts on the availability of suitable rock of the right size from Mt. Schank, and much of the material from Up and Down Rocks may be below size due to thin bedding and irregular dolomitisation. Because no suitable deposits are definitely known within 30 miles of Port MacDonnell it is appropriate at this stage to set down brief comment's on the nature and locality of all the known construction materials within a reasonable distance of the port. The selection of one or more deposits for further testing will then depend upon engineering feasability studies of the more interesting deposits. The deposits are shown on the accompanying locality map.