Australian Iron Formation
This image shows a rock type known as a Banded Iron Formation (BIF). Hopefully the “banded” part makes sense just from the photo.
These rocks are about 2.5 billion years old and come from Dales Gorge in the Pilbara Craton of Western Australia. This is a key time in Earth’s history as it’s when oxygen first began building up in the atmosphere. There are hints from some locations on Earth that bacteria evolved the ability to generate oxygen through photosynthesis hundreds of millions of years earlier, but at around 2.5 billion years ago oxygen started rising.
Before there was oxygen in the atmosphere, iron could exist as “ferrous” iron, with a 2+ charge. When iron rusts today, it becomes “ferric” iron with a 3+ charge – extra oxygen causes the change in charges.
Ferrous iron can dissolve in ocean waters, ferric iron cannot. Prior to oxygen in the atmosphere, iron could dissolve in the oceans, but once oxygen started being generated, the iron dissolved in the world’s oceans reacted with that oxygen and formed sedimentary iron rocks. Many of the world’s economic iron deposits were produced in this way.
The other distinct characteristic of these rocks is their banding. The layers are produced by alternating patterns of iron-rich sediments and silica-rich sediments. The silica rich layers are produced by other sediments which are washed into the areas producing iron formations, possibly by storms, river inputs, or maybe other processes as well.
Image credit: Pete Hill (Creative Commons licensed)
Moh’s hardness scale is perfect for raunchy gemology lessons, let’s face it. We can test all the levels~
i personalized the hardness scale to suit describing an erection im…
This is a work of art.
"he went from fluorite to topaz in 2 seconds"
Opalized fossil Belemite or called Calmari!
These are no ordinary fossils (if there is such a thing): these incredible relics are made of solid opal, sometimes with rainbows of shimmering color. Australia is the only place on Earth where opalized animal fossils are found. These fossils are of global scientific interest and are among the most beautiful and valuable in the world.
How do opalized fossils form?
Opal forms in cavities within rocks. If a cavity has formed because a bone, shell or pine cone was buried in the sand or clay that later became the rock, and conditions are right for opal formation, then the opal forms a fossil replica of the original object that was buried. We get opalized fossils of two kinds:
i. Internal details not preserved: Opal starts as a solution of silica in water. If the silica solution fills an empty space left by a shell, bone etc that has rotted away - like jelly poured into a mould - it may harden to form an opalized cast of the original object. Most opalized shell fossils are ‘jelly mould’ fossils - the outside shape is beautifully preserved, but the opal inside doesn’t record any of the creature’s internal structure.
ii. Internal details preserved: If the buried organic material hasn’t rotted away and a silica solution soaks into it, when the silica hardens it may form an opal replica of the internal structure of the object. This happens sometimes with wood or bone.
Images in this order: Opalized Dinosaur tooth, Ammonite,Shell x2, Dinosaur bone, Wood, Pineapple, Mussel shell, Belemnite. Click on each to view in more detail.
A New Perspective of the Day: This is What a Volcanic Eruption Looks Like from Space
Here’s a striking view of Sarychev Volcano in Kuril Islands of Japan going through its early stage of eruption, taken from the orbit of the International Space Station in June 2009. For more info on this picture, head over to NASA’s Earth Observatory!
Mars Rover Opportunity Finds ‘Rich’ Clay Deposits: “A new study looks at chemicals spotted by a Mars-orbiting spacecraft to conclude that Endeavour Crater, which Opportunity reached in August 2011 after a 1,000-plus day, 13-mile trek across the plains of Meridian, is flush with a variety of clays, which on Earth, form in the presence of water.”
Oh good! Just think: pottery from Mars!
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This is What Happens When Sand Gets Struck by Lightning:
Fulgurites are natural hollow glass tubes formed in quartzose sand, silica, or soil by lightning strikes (at 3,270 °F), which instantaneously melts silica on a conductive surface and fuses grains together over a period of around one second. Photographed by Ken Smith.