Fed Square or Red Square?
Tasks:
- Look closely at the sandstone. Do you notice any differences in the intensity of the red color across different areas? What might explain these variations in color?
- Explain how the red color of the sandstone is formed.
- Why are iron oxides, such as hematite, crucial for the coloration of sandstone? How do water and oxygen contribute to this process?
- Please take a picture of yourself or an object on site to prove your visit and post it with your log.
Log this cache as “Found it” and send me the answers to the questions to “silka03.earthcache@gmail.com”, my profile e-mail or via Geocaching Message Center. Not in your log!
You may then log immediately. I will contact you if something is wrong.
If there are no answers after 14 days I have to delete your log.
Have fun!
At Federation Square in Melbourne, you can observe a fascinating sandstone characterized by its vibrant red, violet, and white patterns. These colors are not only visually striking but also tell a geological story spanning millions of years. This Earthcache invites you to learn more about the formation, composition, and chemical processes that make this rock so unique.
Geological Information:
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What is Sandstone?
Sandstone is a sedimentary rock primarily composed of sand grains, often made of quartz (SiO₂). These grains were deposited by water, wind, or ice and were compressed and cemented over millions of years during a process called diagenesis. The cement binding the sand grains can consist of minerals like silica or iron oxides.
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Why is the Sandstone Red?
The red coloration of this sandstone is caused by the mineral hematite, an iron oxide (chemical formula: Fe₂O₃). During diagenesis, iron present in the rock reacted with oxygen and water, forming hematite. This process is similar to rust formation, where iron oxidizes in the presence of water and oxygen, giving the rock its reddish hue. Hematite coats the sand grains or fills the pores between them.
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Formation of Color Variations:
- Red areas: Contain large amounts of hematite, which either coats the grains or forms part of the cement.
- White areas: Lack significant amounts of iron oxide, indicating different chemical conditions during diagenesis.
- Violet areas: Result from a combination of hematite and other minerals, such as manganese oxides.
These variations reflect different depositional environments and chemical processes during the rock's formation.
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Origin and Age:
The sandstone used at Federation Square likely originates from an Australian quarry, possibly in Queensland or New South Wales. The sediments that formed the sandstone were deposited about 200 to 300 million years ago (Permian to Triassic period). At that time, large river systems and shallow seas covered parts of Australia, leaving behind the sands and clays that eventually became sandstone.
https://de.wikipedia.org/wiki/H%C3%A4matit
https://de.wikipedia.org/wiki/Sandstein
https://de.wikipedia.org/wiki/Rotliegend