***Please bring approximately 1 cup of water with you to help answer the Earth Cache questions.
This Earth Cache has you standing on the edged of a high grade Kaolin Quarry, nearby there should be some pieces of Kaolin that you can pick up and examine.
Kaolin also known as China Clay, White clay, White dirt and Chalk is a soft white clay composed mainly of kaolinite, Al4(OH)8[Si4O10, and other related clay minerals such as nacrite and dickite. Kaolin is considered to be the most important and common mineral in clay used in pre-historic pottery. Kaolin is still very important today, it's apart of our daily lives and we don’t even realise. Perhaps you are using something made with it now?
Kaolin forms in response to anhydrous aluminium silicate alteration in feldspar-rich rocks such as Quartz, which is the most likely source in this case by weathering or hydrothermal processes. The Rock cycle is pictured below; consider Kaolin clay in this circumstance as a sedimentary, the fine particles settle on the bedrock.
The Rock Cycle
The majority of known deposits are primary (residual) or secondary (transported) deposits of Tertiary age. Residual deposits have developed on a variety of lithologies, including granite, slate and volcanic rocks. The highest quality kaolin occurs in residual deposits developed on granite and granitederived transported deposits. The major current sources of high-grade white kaolin in New South Wales are transported deposits associated with the Gulgong Granite, and large sedimentary deposits in the Oaklands–Coorabin area.
Kaolin deposits are commonly classified into two types Primary (residual) deposits formed by in-situ hydrothermal alteration and/or leaching and weathering of such feldspar-rich rocks as granite, syenite or gneiss. Secondary (transported) deposits, these are composed of detrital clay derived from residual deposits formed by sedimentary processes.
In Australia Kaolin deposits started forming during the Late Cretaceous and Tertiary age associated with hot, humid conditions formed thick deposits of high-purity white kaolin, commonly underlying bauxitic laterites. Secondary kaolin generally shows a disordered structure of low crystallinity giving it free slaking, plastic properties, rendering it suitable to applications requiring high degrees of dispersion.
Kaolinitic clay in excess of several meters thick, that occur within Tertiary sediments in the Oaklands–Coorabin area, southern New South Wales, have been mined for use in ceramic (vitreous china), brickmaking and industrial (tile) applications. There, large quantities of kaolin occur within an upper and lower horizon of kaolin separated by medium- to coarse-grained kaolinitic quartz sandstones. Identified resources are about 45 Mt, and potential resources could easily exceed several hundred million tonnes given the large area over which the deposits have been identified.
The physical properties of kaolin can vary depending on the origin of the deposits. Impurities that can affect these properties such as: whiteness, abrasiveness, particle size, shape, viscosity and rheology. These property variances are important in determining the specific applications in which the Kaolin is used.
Approximately 40% of the clay from this mine ends up in Caroma Industries ceramics plant where it is used as a extender, filler and colour enhancer. Many people would have a bathtub, hand basin or toilet that has been manufactured using this product.
The paper industry is one of the biggest consumers of Kaolin, where kaolin is used to fill the spaces between cellulose fibers, and as a coating agent to produce high gloss paper with good printability.
Other uses include clay-based ceramics and refractories, white cement, fibreglass, and fillers and extenders in rubber, paint, plastic and adhesives. Numerous minor uses include pesticide and herbicide carriers, zeolite manufacture, catalyst supports, cat litter, car wash, toothpaste and other pharmaceuticals and cosmetics. Kaolin is readily available and sells for approximately $65kg retail in health food stores and is often used in many skin care and hygiene products because of its innate absorbency abilities and its safe on sensitive skin.
To successfully log this Earth Cache please message us the following answers: ( If you would like to do a basic log to keep your stats and TB distance in order that is fine, but failure to message us the correct answers within 24 hours of such a log will result in the log being deleted.)
1. Take a small piece of Kaolin and pour some water over it, what happens and why?
2. What does dry Kaolin feel like in your hands?
3. Some of the pieces I examined appeared to have small little crystals in them, what possible explanation could there be for tiny crystals being in the Kaolin? Does this suggest it is Primary or Secondary?
4. Redish brown staining can be seen on parts of the Kaolin what has caused that?
5. A photo of your team or GPS with the Quarry in the background. (optional)
We hope you have enjoyed this earth science lesson as much as we enjoyed putting it together we look forward to reading your log.
Sources
http://www.resourcesandenergy.nsw.gov.au/
http://www.n-essentials.com.au/
http://minerals.pir.sa.gov.au/
http://en.wikipedia.org/wiki/Kaolinite
