East Kimberley’s unique zebra rocks protected for future generations

Zebra rock, rainbow stone, astronomite—the entire East Kimberley region is a geological treasure chest.
By Angela Heathcote June 22, 2017 Reading Time: 3 Minutes Print this page

BACK IN 2011, A new deposit of zebra rock was discovered on Newry Station, in the Northern Territory, close to the Western Australian border.

As the name suggests, these geological phenomena exhibit zebra –like stripes in creamy white and orange-red.

Owners of the Kimberley Stone Company, located on Newry, have been operating a boutique mine for the past eight years, fossicking the zebra rock deposit since it was discovered.

On Monday, ABC online reported that the company’s owners and operators, Ruth Duncan and Kim Walker have decided to preserve a particular seam of zebra rock for future generations. This is in addition to creating an area where people are able to view and appreciate the 600 million year old patterned formations.

Kimberley zebra rock is unique. Bruce Livett, owner of the Zebra Rock Gallery in the East Kimberley town of Kununurra, told Australian Geographic that despite its common name WA zebra rock should not be confused with rock of the same name from elsewhere in the world.

“The term ‘zebra rock’ is simply descriptive of the appearance of the rock and says nothing about its composition or how it was formed,” he said. “There are other places where ‘zebra rock’ has been reported but the rock is different in composition to Kimberley zebra rock.

“For example, in Coober Pedy, South Australia, there is a zebra rock but it is sandstone, not a siltstone and is very pale in comparison with the strong bandings displayed on the Kimberley zebra rock.”

Siltstone, which is a sedimentary rock, is typically formed at the base of a river bed. In this case, the zebra rock is a deposit of the Ord River.

“How the banding came about – the separation of the dark iron bands from the pale silica bands —is not known,” Bruce said. “It is one of the mysteries of zebra rock that continues to hold the interest of geologists and collectors.”

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Bruce reveals the striped pattern of the 600 million year old Zebra Rock. (Image Credit: Zebra Rock Gallery)

Lake Argyle, created during the 1960s by the Ord River Irrigation Scheme, was a boon for local agriculture but significant deposits of zebra rock were submerged during its construction.

Now, WA’s longest seam of red-and-creamy stripes is in the Johnny Cake Shale Member of the Ranford Formation, which formed 670 million years ago.

Including the stretches of zebra rock, the Ranford Formation is home to some five types of unique rock: ribbon stone, which exhibits glossy, burnt earth coloured ribbon-like patterns; Okapi, named after another striped animal; astronomite, decorated in small white blotches, contrasted against a dark background, giving the impression you’re holding the galaxy in your hand; and rainbow stone.

The potential of zebra rock in the Kimberly wasn’t realised until Noel Hackett and John Read, leased the area around the old Argyle Downs Homestead in the 1960s to collect the rock and fashion from the deposits, jewellery, stone craft and other decorative items. Before this, Bruce says, the Duracks — pastoral pioneers in the 1800s, used the rock for garden edging.

Bruce, who took over Hackett and Read’s mining lease, says the entire East Kimberley region is a geological treasure chest.

“There are three main attractions and they are the Bungle Bungle range, which don’t occur anywhere else in the world,” he says. “The second is the argyle diamond mine that produces pink diamonds and blue diamonds. And the third geological feature is the presences of these silt stones, which include the zebra rocks.”

The tourist season for the region begins in March and ends in August. Each year the Ranford Formation draws large numbers of tourists, keen to see the geological phenomena of the region.

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Bruce Livett shows off a piece of unpolished zebra rock. (Image Credit: Zebra Rock Gallery)