Introduction:
This is a great little spot to stop either on your way into or leaving Onslow, free camping is allowed and there are signs of fire pits, however no other facilities are available, so remember to do the right thing and leave no trace apart from footprints!
At GZ you will have some nice views of the Hamersley ranges, approximately 13 kms to the east and the flat low lying areas of the coastal plain.
Geology:
Most of the rocks of the Hamersley range are conglomerates, shales and quartzites, but with thick layers of blue asbestos and iron. These rocks formed from marine sediments deposited about 2.4 - 1.8 billion years ago, and were subsequently uplifted and warped. A mature plateau formed during a long period of erosion, after which further uplift rejuvenated the drainage, the water courses then carved gorges along faults and joints.
Quartzite is a nonfoliated, or not having a layered or banded appearence metomorphic rock, composed almost entirely of quartz. It forms when a quartz-rich sandstone is altered by the heat, pressure, and chemical activity of metamorphism.
Metamorphism recrystallizes 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 gray in color. 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. Its extreme toughness made it a favorite rock for use as an impact tool by early people.
When quartzite fractures, it is quite often in a smooth curved way, (cochoidal) and allowes it to be shaped into large cutting tools such as ax heads and scrapers. Its coarse texture made it less suitable for producing tools with fine edges such as knife blades and projectile points. Obsidian, flint and agate were better suited for tools where sharpness was important.
Most quartzite forms during mountain-building events at convergent plate boundaries where sandstone was deposited on a continental plate. There, the sandstone is metamorphosed into quartzite by the intense pressure of a plate collision and often by deep burial. 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 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 large boulders, or as a surface litter of scree. ref:https://geology.com/rocks/quartzite.shtml
To claim your Smilie:
Please answer these questions either via email or the Geocaching messenger app. not in the log!
1. At GZ what is the main colour of the rocks and do you see any quartz?
2. What do you believe is the main reason for this colour?
3. Upload a photo of you, or your GPS with some of the scenery.
Please feel free to log this cache at your earliest coinvienience, however the answers MUST be sent via my profile contact details within 10-12 days or the find log maybe deleted.
Congratulations to adinache for FTF homours!