MV Blog


Banded iron slab

by Kate C
Publish date
11 June 2013
Comments (10)

Early this morning, we installed a huge, beautifully polished slab of banded iron at the entrance of the Dynamic Earth exhibition at Melbourne Museum.

Banded iron slab The banded iron slab showing its gorgeous coloured layers.
Source: Museum Victoria

The slab, donated by stonemason and artist Richard Williamson, is about three metres high and weighs 870 kilograms. Its wavy bands of red jasper and brown iron oxides record the rise of oxygen in the Earth's atmosphere.

About 2.7 billion years ago, the first oxygen-producing cyanobacteria (blue-green algae) completely transformed the Earth by releasing oxygen during photosynthesis. Over hundreds of millions of years, this oxygen reacted with the iron that was dissolved in the ocean, forming solid iron oxides and silica which settled on the ocean floor. It was only once all the iron precipitated out of the oceans that oxygen began to build in the atmosphere, and the Earth became habitable for multicellular life forms like us. There is, however, approximately 20 times more oxygen within the banded iron formations than is present in the atmosphere today.

  Banded iron slab installation The slab resting on its A-frame and about to be positioned with the slab lifter.
Image: Heath Warwick
Source: Museum Victoria

This piece of banded iron formed about 2.5 billion years ago in the area that is now the Pilbara in Western Australia. It was subsequently buried and metamorphosed, or transformed under extreme pressure, changing the minerals and creating the folds and waves of its layers. Among the red bands of fine-grained silica called jasper, and black layers of iron oxide, you can see shimmery yellow lines of tiger-eye, a fine-grained quartz that has replaced a fibrous mineral.

team installing rock slab Ant, Nev and Veegan using the folklift to lift the 870kg slab and guiding it into its support brackets.
Image: Heath Warwick
Source: Museum Victoria

Banded iron is the major source of the world's iron ore. Most of these large iron ore deposits formed between 2.5 and 1.8 billion years ago. It is mined and fed into blast furnaces to extract the metal. This piece escaped that fate because of its unusual beauty and size; it is rare to find such a large piece that has no veins of quartz, which often cause fractures. The rock, once a huge boulder, was extracted from the Ord Ridley Ranges, cut in Perth and polished in Adelaide.

installing the rock slab View through the dinosaurs of the slab in its new home.
Image: Heath Warwick
Source: Museum Victoria

Installing such a huge specimen was quite a feat. In the wall behind the rock, steel supports and counterweights hold it securely in place. Bringing it into the gallery took a team of people and a forklift designed to lift and move concrete slabs for building construction. The crew brought the slab in on an A-frame trolley, lifted it, and inched it carefully into its specially-designed support brackets.

And yes, you can touch it!

Dermot with the banded iron slab Manager of Natural Science Collections Dermot Henry next to the newly-installed slab of banded iron.
Image: Heath Warwick
Source: Museum Victoria

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Updates on what's happening at Melbourne Museum, the Immigration Museum, Scienceworks, the Royal Exhibition Building, and beyond.