Zebra rock is a strange patterned silt stone (siliceous argillite) unique to the Ranford formation in the Kununurra district in the East Kimberley region of Western Australia. The deposit is 600 million years old, placing it in the Upper Proterozoic era or Pre-Cambrian period. It has a very fine texture, like that of unglazed porcelain. The dark spots have the same texture as the light areas, and are colored by Hematite (iron oxide). The formation of the spots is mysterious, but is clearly the result of a three-dimensional reaction-diffusion type instability. Other, more exotic explanations have been proposed.

 The scale of the stripes/spots is about 1cm.

 Special thanks to Sasha Golovin for giving me this sample.
 
 

Some photos of Zebra Rock

Click on image for larger view
• Front side of a slab.
• back side.
• Two more photos of a smaller sample:[front][back].

References and Links

• E. Mattievich, J. Chadwick, J.D. Cashion, J.F. Boas, M.J. Clark and R.D. Mackie, "Macroscopic ferronematic liquid crystals determine the structure of Kimberley Zebra Rock", proceedings of the 27th annual A&NZIP condensed matter and materials meeting, Feb 2003, Wagga Wagga NSW, [online paper].

• F.C. Loughnan and F.I. Roberts, Australian Journal of Earth Sciences, vol. 37, p. 201 (1990).
• R. A. Hobson, Journal of the Royal Society of Western Australia, vol. XVI, pp. 57-70 (1930).
• David W. Trainer, Jr., "Zebra Rock", American Minerologist, Vol. 16, p. 221-225 (1931). [online version].
• Peter J. Ortoleva, "Geochemical self-organization", ( New York, Oxford University Press, 1994). [online info].

• H. Bracewell, Gems around Australia. Part 5 [Zebra stone]. Australian Gemmologist, Vol. 17, p. 454-456 (1991). [page image in pdf]
• H.-J. Krug, H. Brandtstädter, K. H. Jacob, "Morphological instabilities in pattern formation by precipitation and crystallization processes", Geologische Rundschau, Vol. 85, p. 19-28 (1996).
• Article from the Earth Museum at the University of Western Australia [pdf]. Good photo.
• Shards of zebra rock: an image from Ben and Andrea's travel blog.
• An article about Zebra Rock by Jan and Max Hedger.
• The Zebra Rock Gallery, P.O. Box 97, Kununurra, Western Australia, 6743.



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