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First discovered in 1924, Zebra rock is a marketing name for an Australian decorative stone that has an appearance of varying brown and white bands. Unlike other mineral specimens, Zebra rock is a silt stone that is formed by the deposition of very fine silt carried out by running water.
Zebra rock was naturally formed about 1.2 billion years ago, and is currently only found in an area of Western Australia that is south to Kununurra, near the Lake Argyle catchment area1.
While Zebra rock is mainly composed of fine grained quartz and sericite, minor amounts of alunite, kaolinite clay and dickite are also found within this mineral. Several patterns appear to Zebra rock, some of which include bands, rods, irregular blebs that run through the rock in parallel rows, thereby creating regularly spaced ferruginous brown bands, or spots on a white to pale brown clay-rich matrix.
The color banding of the Zebra rock is believed to be formed by the rhythmic precipitation of hematite, or more commonly known as iron oxide, rich bands by the migration of percolation fluids through the rock during the alteration of the rock2.
The thickness of the beds determines the width of the bands that are present within the Zebra rock. As a result of the beautiful patterns present on this mineral, Zebra rock is widely sold as a decorative stone in local and international markets.
The fine-grained Zebra stone is soft enough to be sculpted into various shapes by simple mechanical methods utilizing hand tools. These incredible and gorgeous decorative stones are mined by creating a trench using an excavator, in which subsequent removal of the zebra rock is taken in blocks and later sculpted for various purposes.
During the wet season in Australia, the Zebra rock is under water, therefore, its mining can only take place for a period of ten weeks during late October or early November.
The collected blocks are then cut using rock saws and sculpted into various decorative objects and smaller objects using diamond saws and diamond grinders1. Since no two pieces of Zebra rock are the same, the objects that are sculpted from the rocks have their own unique individual pattern.
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Some of the products made using Zebra rocks include wine racks, coaster sets, bowls, animal sculptures and jewelry such as necklaces, bracelets, among various others. These items are then finished with ultra-fine wet and dry emery paper in order to impart a smooth semi-glossy and lustrous look to the product.
Since Zebra rock is a silt stone, it is porous to water, therefore, it can absorb moisture from the atmosphere. To preserve the colors of the mineral and maintain the contrast of the rock bandings, these decorative items are often sealed with warm Vaseline or talcum powder, and finally coated with several layers of polyurethane solvent. The sealers are used to enhance the color and improve the elegance of the finished products.
In 2011, a new deposit of Zebra rock was discovered on Newry station, which is about 70 kilometers away from Kununurra. The Kimberley mining company started mining for this rare stone to create highly valued decorative objects and ornaments3.
On June 18th, 2017, the owners of the mine, Ruth Duncan and Kin Walker, decided to stop mining at its biggest deposit in order preserve this site for the future generations4. The couple plans to polish this site and create a viewing area for people to witness the amazing rock formation. Geologists from around the world come and visit the mine to witness the stunning patterns of the naturally formed Zebra rock.
The patterns present within the Zebra rock mineral are extremely complicated, yet mathematically perfect, and geologists are astounded to see these rocks in person, while simultaneously attempting to investigate how nature could create such incredibly perfect and complicated patterns.
Outside of the geology community, a large-scale viewing area of these incredible rock formations will hopefully attract attention from tourists around the world to visit and learn about the wondrous Zebra rock, and how its preservation surpasses the worth of any household item it could be used to create.
References:
- “Zebra rock (zebra stone) deposits” – Mindat.org
- “Zebra Rock” – Government of Western Australia
- “Rare Zebra Rock being mined on Territory cattle station” – ABC News
- “Mining company chooses to protect rare deposit of zebra rock rather than mine it” – ABC News
- Shutterstock.com/AnitaPotter
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