Banded iron slab

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by Kate C
Publish date
11 June 2013
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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
 

Comments (10)

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JessB 11 June, 2013 17:50
Wow, that is really amazing! Isn't it wonderful what time and pressure can do?!
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Sara G 11 June, 2013 18:01
My kids are going to love seeing it... and being able to touch it :)
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Alice 12 June, 2013 14:26
Damn, my boofy head is in the way of that third shot :(
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Imbootoo 13 June, 2013 14:44
Wonderful gift to your museum - an amazing treasure that captures the history of the earth in a slab of stone! Thank you for providing the explanations as to how it was formed. I love this type of stone; we have it in Wyoming in the desert.
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Siobhan 14 June, 2013 21:24
I took a few moments to come up and have a look at this today. Congratulations to the team, this is a really wonderful addition to the gallery.
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Sue M 17 June, 2013 10:20
An amazing gift to Australia Richard. How fortunate are we to have people like you in our world. Thank you.
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richard 26 June, 2013 23:28
Hi Sue, Comments like yours make all that work and effort worthwhile. Thank you.
Darren 24 June, 2013 10:00
Wow! 2.5 billion years... That's a little over half the age of Earth as we know it... Hope to see this fine specimen this weekend!!
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Guida the Bestest 28 June, 2013 11:36
It is humbling to see an object of such great age and beauty. Thankyou for your genorosity Richard Williamson.
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Les 28 June, 2013 14:41
When I first saw this magnificent display I was gob smacked. Thank you for the detailed explanation on its formation. I can now confidently impart that knowledge to our visitors.
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