The 600 million year old mystery

Visitors to the Kimberley Region of Western Australia leave with memories of a formidable, rugged landscape – an ancient land holding many mysteries and well kept secrets.

Some 600 million years ago when the only life on earth was simple aquatic organisms and Australia was still part of the super-continent Gondwanaland, layers of a striking red and while banded stone were formed near where Kununurra is today. The sparsely distributed seams of Zebra Stone are the only known deposits of this rare and beautiful material.

Zebra Stone is an indurated siltstone, altered from its original sedimentary form by unknown geological and chemical processes. It was first documented in 1924 following its discovery close to the Durack homestead on the Argyle pastoral lease.

Only a small portion of the total deposits remained above water following the construction of Lake Argyle in 1972. Reserves are measured in kilos rather than tonnes, with some patterns yielding only a few kilos. Seams are tightly enclosed in shale, varying in width from 25mm to 400mm. The regularly curved bands and rods disappear and reoccur at intervals within the seam, making recovery expensive and tedious.

The curved banding of red and white occurs at nearly right angles to the bedding plane. Analysis of samples has disclosed an extraordinary number and range of elements, including rare earths, adding to its wonder and contributing to its unique texture and qualities.

Although it is compact and fine grained Zebra Stone is soft enough to cut and carve with hand tools, lending itself to finishing with fine wet and dry emery paper. Coating with a clear spray-on sealer, either satin or gloss, avoids smudging of the iron oxides in the material.