The shore at the bottom of Melville Bay is stated by Captain Flinders to consist of low cliffs of pipe-clay, for a space of about eight miles in extent from east to west; and similar cliffs of pipe-clay are described as occurring at Goulburn Islands (see the plate, volume 1) and at Lethbridge Bay, on the north of Melville Island: both of which places are considerably to the west of the Gulf of Carpentaria.
Morgan's Island, a small islet in Blue-Mud Bay, on the north-west of Groote Eylandt, is composed of clink-stone; and other rocks of the trap-formation occur in several places on this coast.
The north of Blue-Mud Bay has furnished also specimens of ancient sandstone; with columnar rocks, probably of clink-stone.

Round Hill, near Point Grindall, a promontory on the north of Morgan's Island, is composed, at the base, of granite; and Mount Caledon, on the west side of Caledon Bay, seems likewise to consist of that rock, as does also Melville Island.

This part of the coast has afforded the ferruginous oxide of manganese: and brown hematite is found hereabouts in considerable quantity, on the shore at the base of the cliffs; forming the cement of a breccia, which contains fragments of sandstone, and in which the ferruginous matter appears to be of very recent production; resembling, perhaps, the hematite observed at Edinburgh by Professor Jameson, around cast-iron pipes which had lain for some time in sand.* (*Footnote.

Edinburgh Philosophical Journal, July 1825 page 193.) The general range of the coast, it will be observed, from Limmen's Bight to Cape Arnhem, is from south-west to north-east; and three conspicuous ranges of islands on the north-western entrance of the Gulf of Carpentaria, the appearance of which is so remarkable as to have attracted the attention of Captain Flinders,* have the same general direction: a fact which is probably not unconnected with the general structure of the country.

The prevailing rock in all these islands appears to be sandstone.
(Flinders Volume 2 page 158.