Our aim with this particular Earth Cache is to take you to an scenic spot and teach you some basics, we have presented this earth science lesson on a basic level to accommodate those who avoid EC’s ‘cos they are too hard’ and also to accommodate those travelling with Children (TAWKers) who incorporate Earth caches into their curriculum.
*A quick experiment is required at GZ please bring a nail, pocket knife or similar hard metal object with you.
A visit to Kununurra isn’t complete without coming out to the iconic Ivanhoe Crossing. For those who haven’t heard of the crossing or the tall tales and legends of the crossing; it is a concrete causeway over the Ord River, north of Kununurra, originally part of the main road through to Wyndham. Since the start of the Ord irrigation project in the 1960's, the river now flows all year round, making the crossing impassable during the "Wet season" when the river level is higher.
Please be croc safe, the viral Internet video of the Croc towing a full size cow down a river last year was shot just downstream from here.
As the river fluctuates the posted coordinates are merely a suggestion (we also quiet liked how the southing and easting minutes married up). Your observations can be made from anywhere along the causeway, please remember to be safe.
Today’s Earth Science lesson is about Quartzite.
Quartzite is a metamorphic rock composed almost entirely of quartz. It forms when a quartz-rich sandstone is altered by the heat, pressure, and chemical activity of metamorphism. These conditions recrystallize the sand grains and the silica cement that binds them together. The result is a network of interlocking quartz grains of incredible strength.
The interlocking crystalline structure of quartzite makes it a hard, tough, durable rock. It is so tough that it breaks through the quartz grains rather than breaking along the boundaries between them. This is a characteristic that separates true quartzite from sandstone.
Quartzite is usually white to grey in colour. Some rock units that are stained by iron can be pink, red, or purple. Other impurities can cause quartzite to be yellow, orange, brown, green, or blue.
The quartz content of quartzite gives it a hardness of about seven on the Mohs Hardness Scale.
Quartzite’s extreme toughness made it a chosen rock for use as an impact tool by Aboriginal people. Its conchoidal fracture allowed it to be shaped into large cutting tools. Its coarse texture made it less suitable for producing tools with fine edges such as smallblades and projectile points.
Most quartzite forms during mountain-building events at convergent plate boundaries. There, sandstone is metamorphosed into quartzite while deeply buried. Compressional forces at the plate boundary fold and fault the rocks and thicken the crust into a mountain range. Quartzite is an important rock type in folded mountain ranges throughout the world.
Quartzite is one of the most physically durable and chemically resistant rocks found at Earth's surface. When the mountain ranges are worn down by weathering and erosion, less-resistant and less-durable rocks are destroyed, but the quartzite remains. This is why quartzite is so often the rock found at the crests of mountain ranges and covering their flanks as a litter of scree.
Quartzite is also a poor soil-former. Unlike feldspars which break down to form clay minerals, the weathering debris of quartzite is quartz. It is therefore not a rock type that contributes well to soil formation. For that reason it is often found as exposed bedrock with little or no soil cover.
What are Metamorphic Rocks?
Metamorphic rocks have been modified by heat, pressure, and chemical processes, usually while buried deep below Earth's surface. Exposure to these extreme conditions has altered the mineralogy, texture, and chemical composition of the rocks.
There are two basic types of metamorphic rocks. Foliated metamorphic rocks such as gneiss, phyllite, schist, and slate have a layered or banded appearance that is produced by exposure to heat and directed pressure.
Non-foliated metamorphic rocks such as hornfels, marble, quartzite, and novaculite do not have a layered or banded appearance.
To log this Earth Cache we require you to visit GZ and make some observations, consider the information given, then message us with the following answers to the best of your ability;
1. Looking out into the river can you see any Quartzite? Describe the size and Colour. (This is dependant on the river level, if the river it too high try to observe Quartzite along the banks.)
2. Find a rock nearby that you can easily touch, perform a basic hardness test by scratching the surface of the rock with an implement. From these basic results and your observations can you draw the conclusion that this rock is Quartzite? (fingernail and car key/pocket knife will be fine)
3. Is Quartzite Non-foliated or foliated metamorphic rock?
4. A photo of your team or GPS near the causeway, upload as many photos as you like! (Optional)
You are welcome to log your answers straight away to keep your TB's and Stats in order but please message us with your answers within 1 week. Cachers who do not fulfil the Earth Cache requirement will have their logs deleted without notice.
Source: Geology.com, Wikipedia.
