Devils Marbles - a nearly perfectly circular shaped boulder of red granite is balanced on a hugh rock with a small crevice filled with water . Devils Marbles Conservation Area, Northern Territory, Australia. A spectacular formation of huge granite boulders spread across a wide shallow valley. They owe their creation to the circulation of day and night; respectively the very hot day temperatures and bitter cold desert nights. Because of those hugh differences in temperature; giant granite boulders expanded and shrinked in size continually. As a result the surfaces of these blocks flaked off like onion pellicles; and still does.